Range extension in wireless local area networks

ABSTRACT

A method for associating a new end-station (end-STA) with a relay access point (R-AP) in a relay transmission. An assignment of a new identifier is transmitted to the new end-STA, wherein traffic indication map indications for the new end-STA in a beacon from the R-AP follows the transmission of the new identifier assignment. A message is sent to a root access point (AP), the message including an indication of a number of information fields in the message and at least one information field, each of the at least one information fields including an identifier of one end-STA associated with the R-AP. An acknowledgement is received from the root AP on a condition that the root AP correctly receives the message and associates an identifier of the end-STA with an identifier of the R-AP.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/751,646, filed Jan. 11, 2013, U.S. Provisional PatentApplication No. 61/774,310, filed Mar. 7, 2013, and U.S. ProvisionalPatent Application No. 61/832,102, filed Jun. 6, 2013, all of which areincorporated by reference as if fully set forth herein.

BACKGROUND

A wireless local area network (WLAN) in Infrastructure basic service set(BSS) mode has an Access Point (AP) for the BSS and one or more stations(STAs) associated with the AP. The AP typically has access or interfaceto a distribution system (DS) or another type of wired/wireless networkthat carries traffic into and out of the BSS. Traffic to STAs thatoriginates from outside the BSS arrives through the AP and is deliveredto the STAs. Traffic originating from STAs to destinations outside theBSS is sent to the AP to be delivered to the respective destinations.Traffic between STAs within the BSS may also be sent through the APwhere the source STA sends traffic to the AP and the AP delivers thetraffic to the destination STA. Such traffic between STAs within a BSSis really peer-to-peer traffic. Such peer-to-peer traffic may also besent directly between the source and destination STAs with a direct linksetup (DLS) using an 802.11e DLS or an 802.11z tunneled DLS (TDLS). AWLAN in Independent BSS mode has no AP and STAs communicate directlywith each other.

New spectrum is being allocated in various countries around the worldfor wireless communication systems such as WLANs. Such spectrum is oftenlimited in the size and bandwidth of the channels they comprise. Inaddition, the spectrum may be fragmented in that available channels maynot be adjacent and may not be combined for larger bandwidthtransmissions. Such is the case, for example, in spectrum allocatedbelow 1 GHz in various countries. WLAN systems, for example built on the802.11 standard, may be designed to operate in such spectrum. Giventhese limitations, the WLAN systems will only be able to support smallerbandwidths and lower data rates compared to high throughput (HT)/veryhigh throughput (VHT) WLAN systems, for example, based on the802.11n/802.11ac standards.

The IEEE 802.11ah Task Group (TG) has been established to developsolutions to support WLAN systems in the sub-1 GHz band and to achievethe following requirements: orthogonal frequency division multiplexing(OFDM) physical (PHY) layer operating below 1 GHz in license-exemptbands excluding television white space (TVWS); enhancements to themedium access control (MAC) layer to support the PHY and coexistencewith other systems; and optimization of rate versus range performance(range up to 1 km (outdoor) and data rates greater than 100 Kbit/s).

The following use cases have been adopted: sensors and meters; backhaulsensor and meter data; and extended range WiFi for cellular offloading.The spectrum allocation in some countries is limited. Therefore, thereis a need to support a 1 MHz only option in addition to support for a 2MHz option with a 1 MHz mode. The 802.11ah PHY is required to support 1,2, 4, 8, and 16 MHz bandwidths.

The 802.11ah PHY operates below 1 GHz and is based on the 802.11ac PHY.To accommodate the narrow bandwidths required by 802.11ah, the 802.11acPHY is down-clocked by a factor of 10. While support for 2, 4, 8, and 16MHz bandwidths may be achieved by the 1/10 down-clocking support for the1 MHz bandwidth requires a new PHY definition with a Fast FourierTransform (FFT) size of 32.

In the sensors and meters use case, up to 6000 STAs are supported withinone BSS. The devices such as smart meters and sensors have differentrequirements pertaining to the supported uplink and downlink traffic.For example, sensors and meters may be configured to periodically uploadtheir data to a server which will most likely to be uplink traffic only.Sensors and meters may also be queried or configured by the server. Whenthe server queries or configures a sensor or meter, it will expect thatthe queried data should arrive within a setup interval. Similarly, theserver/application will expect a confirmation for any configurationperformed within a certain interval. These types of traffic patterns aredifferent than the traditional traffic patterns assumed for WLANsystems.

In the signal (SIG) field of the physical layer convergence procedure(PLCP) preamble of a packet, two bits are used to indicate the type ofacknowledgment (ACK) expected as a response (i.e., early ACK indication)to the packet: ACK (“00” value), block ACK (BA) (“01” value), no ACK(“10” value), and that a packet will be transmitted in the followingframe (“11” value).

High Efficiency WLAN (HEW) is directed to enhancing the Quality ofExperience (QoE) for a broad spectrum of wireless users in many usagescenarios, including high-density scenarios in the 2.4 GHz and 5 GHzbands. New use cases which support dense deployments of APs and STAs,and associated Radio Resource Management (RRM) technologies are beingconsidered. Potential applications for HEW include usage scenarios suchas: data delivery for stadium events, high user density scenarios suchas train stations or enterprise/retail environments, an increaseddependence on video delivery, and wireless services for medicalapplications.

SUMMARY

A method for associating a new end-station (end-STA) with a relay accesspoint (R-AP) in a relay transmission. An assignment of a new identifieris transmitted to the new end-STA, wherein traffic indication mapindications for the new end-STA in a beacon from the R-AP follows thetransmission of the new identifier assignment. A message is sent to aroot access point (AP), the message including an indication of a numberof information fields in the message and at least one information field,each of the at least one information fields including an identifier ofone end-STA associated with the R-AP. An acknowledgement is receivedfrom the root AP on a condition that the root AP correctly receives themessage and associates an identifier of the end-STA with an identifierof the R-AP.

A relay access point (R-AP) includes a processor, a transmitter, and areceiver. The processor is configured to assign a new identifier to anew end-station (end-STA) associated with the R-AP. The transmitterconfigured to transmit the new identifier to the new end-STA, whereintraffic indication map indications for the new end-STA in a beacon fromthe R-AP follows the transmission of the new identifier assignment; andsend a message to a root access point (AP), the message including anindication of a number of information fields in the message and at leastone information field, each of the at least one information fieldsincluding an identifier of one end-STA associated with the R-AP. Thereceiver is configured to receive an acknowledgement from the root AP ona condition that the root AP correctly receives the message andassociates an identifier of the end-STA with an identifier of the R-AP.

An information element (IE) for use in a relay transmission includes anindication of a number of information fields in the IE and eachinformation field including an identifier of one end-station (end-STA).

A method for use in a relay access point (R-AP) is described. The R-APcommunicates with a plurality of end-stations (end-STAs), each end-STAhaving a medium access control (MAC) address. A determination is madethat a new end-STA has associated with the R-AP. A message is generatedfor transmission to a root access point (AP), the message including aMAC address of each of the plurality of end-STAs and a MAC address ofthe new end-STA, and the message is transmitted to the root AP.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings,wherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 is a signal diagram of a downlink relay with an explicit ACK;

FIG. 3 is a signal diagram of an uplink relay with an explicit ACK;

FIG. 4 is a diagram of a Relay Element format;

FIG. 5 is a signal diagram of downlink data retrieval for relay using atraffic indication map (TIM)-based retrieval;

FIG. 6 is a signal diagram of downlink data retrieval for relay using arelay-initiated retrieval;

FIG. 7 is a signal diagram of relay flow control in the downlink for adata/ACK frame sequence;

FIG. 8 is a signal diagram of relay flow control in the uplink for adata/ACK frame sequence;

FIG. 9 is a signal diagram of relay flow control in the downlink for anaggregated medium access control protocol data unit (A-MPDU)/BA framesequence;

FIG. 10 is a signal diagram of relay flow control in the uplink for anA-MPDU/BA frame sequence;

FIG. 11 is a diagram of a short/null data packet (NDP) relay stop frameformat;

FIG. 12 is a diagram of a short/NDP relay start frame format;

FIG. 13 is a signal diagram of network allocation vector (NAV) settingfor relay in a case of a successful data transmission;

FIG. 14 is a signal diagram of a second NAV setting for relay in a caseof a successful data transmission;

FIG. 15 is a signal diagram of a third NAV setting for relay in a caseof a successful data transmission;

FIG. 16 is a signal diagram of a fourth NAV setting for relay in a caseof a successful data transmission;

FIG. 17 is a diagram of an end-STA report information element (IE);

FIG. 18 is a signal diagram for an implicit ACK for an A-MSDU from thedistribution system (DS);

FIG. 19 is a signal diagram for an alternate implicit ACK for an A-MSDUfrom the DS;

FIG. 20 is a signal diagram for an implicit ACK for a 1 MHz mode relay;

FIG. 21 is a signal diagram for an alternate implicit ACK for a 1 MHzmode relay;

FIG. 22 is a signal diagram of an ACK forwarding scheme;

FIG. 23 is a signal diagram of an end-to-end block ACK scheme;

FIG. 24 is a signal diagram of a Speed Frame Exchange operation forrelay;

FIG. 25 is a signal diagram of an alternate Speed Frame Exchangeoperation for relay;

FIG. 26 is a signal diagram of a Speed Frame Exchange operation forrelay using a Speed Frame Exchange Continue (SFEC) field;

FIG. 27 is a signal diagram of an alternate Speed Frame Exchangeoperation for relay using a SFEC field; and

FIG. 28 is a diagram of a Relay Control IE format.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal frequency divisionmultiplexing, orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA),and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a Node-B, an eNode B,a Home Node B, a Home eNode B, a site controller, an access point (AP),a wireless router, and the like. While the base stations 114 a, 114 bare each depicted as a single element, it will be appreciated that thebase stations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple-output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDM, OFDMA, SC-FDMA, and the like.For example, the base station 114 a in the RAN 104 and the WTRUs 102 a,102 b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (WLAN),802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)),CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000),Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), GlobalSystem for Mobile communications (GSM), Enhanced Data rates for GSMEvolution (EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 106.

The RAN 104 may include eNode-Bs 140 a, 140 b, 140 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 140 a, 140 b, 140c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 140 a, 140 b, 140 c may implement MIMO technology. Thus,the eNode-B 140 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 140 a, 140 b, 140 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1C, theeNode-Bs 140 a, 140 b, 140 c may communicate with one another over an X2interface.

The core network 106 shown in FIG. 1C may include a mobility managementgateway (MME) 142, a serving gateway 144, and a packet data network(PDN) gateway 146. While each of the foregoing elements are depicted aspart of the core network 106, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 142 may be connected to each of the eNode-Bs 142 a, 142 b, 142 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 142 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 144 may be connected to each of the eNode Bs 140 a,140 b, 140 c in the RAN 104 via the S1 interface. The serving gateway144 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 144 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 144 may also be connected to the PDN gateway 146,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices. An access router (AR) 150 of a wireless local area network(WLAN) 155 may be in communication with the Internet 110. The AR 150 mayfacilitate communications between APs 160 a, 160 b, and 160 c. The APs160 a, 160 b, and 160 c may be in communication with STAs 170 a, 170 b,and 170 c.

The core network 106 may facilitate communications with other networks.For example, the core network 106 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 106 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 106 and the PSTN 108. In addition, the corenetwork 106 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

To serve STAs with poor wireless link conditions more efficiently withrespect to the power budget, relay functionality was introduced. A relaynode allows range extension and supports packet/frame forwarding betweensource and destination nodes. A relay node is a device that may includetwo logical entities: a relay STA (R-STA) and a relay AP (R-AP). TheR-STA associates with a parent node or AP. The R-AP allows STAs toassociate and obtain connectivity to the parent node/AP via the R-STA.

A simple bidirectional two-hop relay function has been proposed usingone relay node. Two-hop relaying uses a bidirectional relay function,reduces power consumption on the STA with battery constraints, has alimited modulation and coding set (MCS) range, shares one transmitopportunity (TXOP) to reduce the number of contentions for channelaccess, uses address buffer overflow at the relay node with a flowcontrol mechanism, uses a probe request for relay node discovery, andincludes information on the AP-STA link budget (if available) to reducethe number of responses.

FIG. 2 is a signal diagram of a downlink relay procedure 200 from an AP(source) to a STA (destination) through a relay node. The procedure 200is performed between an AP 202, a relay node 204, and a STA 206. The AP202 sends a downlink data frame 210 with the early ACK indication bitsset to “00” to the relay node 204 (step 230). After a short interframespace (SIFS) interval 212, the relay node 204 sends an ACK 214 to the AP202 and sets the early ACK indication bits for the next outgoing frameto “11” (step 232). After receiving the ACK 214, the AP 202 removes thedata frame 210 from its transmission buffer and defers for a period oftime equal to: MAX_PPDU+ACK+(2×SIFS) before the next event (step 234).

After a second SIFS interval 216, the relay node 204 sends a data frame218 to the STA 206 (step 236). The relay node 204 sends the data frame218 with a different MCS than was used for the data frame 210 and setsthe early ACK indication bits to “00.” The relay node 204 buffers thedata frame 218 until successful delivery to the STA 206 or until a retrylimit is reached. If the STA 206 successfully receives the data frame218, after a third SIFS interval 220, the STA 206 sends an ACK 222 tothe relay node 204, with the early ACK indication bits set to “10” (step238).

FIG. 3 is a signal diagram of an uplink relay method 300 from a STA(source) to an AP (destination) through a relay node. The method 300 isperformed between an AP 302, a relay node 304, and a STA 306. The STA306 sends an uplink data frame 310 with the early ACK indication bitsset to “00” to the relay node 304 (step 330). After a SIFS interval 312,the relay node 304 sends an ACK 314 to the STA 306 and sets the earlyACK indication bits for the next outgoing frame to “11” (step 332).After receiving the ACK 314, the STA 306 removes the data frame 310 fromits transmission buffer and defers for a period of time equal to:MAX_PPDU+ACK+(2×SIFS) before the next event (step 334).

After a second SIFS interval 316, the relay node 304 sends a data frame318 to the AP 302 (step 336). The relay node 304 sends the data frame318 with a different MCS than was used for the data frame 310 and setsthe early ACK indication bits to “00.” The relay node 304 buffers thedata frame 318 until successful delivery to the AP 302 or until a retrylimit is reached. If the AP 302 successfully receives the data frame318, after a third SIFS interval 320, the AP 302 sends an ACK 322 to therelay node 304, with the early ACK indication bits set to “10” (step338).

A Relay Element is defined for using in connection with the relayoperation and may be used with any of the embodiments described herein.A STA with dot11RelaySTACapable set to true includes the Relay Elementin an association request or a probe request, for example. The RelayElement contains parameters to support the relay operation. FIG. 4 showsa Relay Element format 400, including an element ID field 402, a lengthfield 404, a Relay Control field 406, and a root AP BSSID field 408.

The element ID field 402 includes an identified for the Relay Element400. The length field 404 includes a length of the Relay Element 400.The Relay Control field 406 indicates whether the AP is a root AP orwhether it relays an SSID, as specified in Table 1.

TABLE 1 Relay Control Meaning 0 Root AP 1 Relayed SSID 2-255 Reserved

The rootAP BSSID field 408 indicates the BSSID of the root AP.

A STA paged via a traffic indication map (TIM) is implicitly assigned arestricted access window (RAW) slot. The AP allocates an equal-lengthtime slot for the STA to send a PS-Poll frame and to retrieve thedownlink (DL) data.

RAW slot index f(x)=(x+N _(offset))mod N _(RAW)   Equation (1)

N_(RAW)=T_(RAW)/T_(S), where T_(RAW) is the entire RAW duration, T_(S)is the duration of one RAW slot, and x is the position index of a pagedSTA or association identifier (AID).

With relay being used, the end-STA (the destination STA in a relayprocedure) takes more time to send the PS-Poll and retrieve the DL data,causing time slot misalignment for all STAs (relay or non-relay), andthe current implicit time slot allocation method does not work. For asystem that uses relay functions, there are two issues: the assigned RAWslot of a regular STA may collide with the beacon/TIM transmitted by aR-AP, and the assigned RAW slot of the end-STA may collide with the RAWslot of other STAs because when the end-STA receives the RAW slotinformation it is delayed by the relay.

Therefore, methods to resolve the collision of the RAW slot are requiredto ensure proper DL data retrieval, and a procedure for the end-STAusing relay to retrieve DL data via TIM that can keep the currentprocedures for non-relay STA intact is desired.

FIG. 5 is a signal diagram of downlink data retrieval method 500 forrelay using a two-step traffic indication map (TIM)-based DL dataretrieval. The method 500 is performed between an AP 502, a relay node n504, a STA m 506, a first end-STA p 508, and a second end-STA q 510. Themethod 500 includes two stages: stage 1 520 is a TIM-based DL dataretrieval between the root AP and STAs (including relay nodes)associated to the root AP, and stage 2 522 is a TIM-based DL dataretrieval between the relay node and end-STAs associated to the relaynode.

In stage 1 520, the relay node retrieves the DL data from the AP onbehalf of the end-STA using the TIM. The AP 502 broadcasts a TIM 530with a positive indication of DL data buffered at the AP for STAs 506,508, 510. The positive indication in the TIM 530 may be set using one ofthe following approaches. A positive indication in the TIM 530 isreflected on the AID of each end-STA 508, 510 that is associated throughthe relay node 504. Alternately, a positive indication in the TIM 530 isreflected on the AID of the relay node 504 if at least one end-STA thatis associated through the relay node 504 has DL data buffered at the AP502, then the AP 502 sets a positive indication for the relay node 504in the TIM 530. Alternately, a positive indication in the TIM 530 isindicated by using a broadcast side channel from the AP 502, which maybe specific to a group of STAs associated through the relay node 504.

Upon receiving a positive indication in the TIM 530 for its own AID, orat least one positive indication for the AID of end-STAs associated withit, the relay node 504 (the R-STA entity within it) sends a PS-Pollframe 532, or similar management frame, in the UL to retrieve the DLdata from the AP 502 on behalf of the end-STA(s). In the case where therelay node 504 receives more than one positive indication for the AID ofend-STAs associated with it, the relay node 504 may choose to implementone or more of the following procedures.

The relay node 504 sends a PS-Poll frame 532 for each end-STA associatedwith the relay node with a positive indication in a one-by-one manner.The AID/Duration field in the PS-Poll frame 532 is set to the AID of theend-STA, which is different than the transmitter address (TA) in thePS-Poll frame.

Alternately, the relay node 504 sends a PS-Poll frame 532 for allend-STAs associated with the relay node with a positive indication. TheAID/Duration field in the PS-Poll frame 532 is set to a special valuewhich represents “all end-STAs.”

Alternately, the relay node 504 sends a PS-Poll frame 532 for eachsubset of all end-STAs associated with the relay node with a positiveindication in a subset-by-subset manner. The AID/Duration field in thePS-Poll frame 532 may be reused to signal the subset of associatedend-STAs.

Upon receiving the PS-Poll frame 532 from the relay node 504 retrievingDL data for one or several end-STAs, the AP 502 sends the DL data 534 asa medium access control (MAC) protocol data unit (MPDU) for one end-STAor as an aggregate MPDU (A-MPDU) for several end-STAs to the relay node504.

If the relay node 504 receives the DL data 534 for the end-STA from theAP correctly, it sends an ACK 536 and sets the ACK indication bits. Asan example, the relay node 504 may set the ACK indication bits to “10”for the next outgoing frame. This may be interpreted by the AP 502 thatthe relay node 504 will not forward the DL data 536 to the correspondingend-STA immediately because it may be in a sleep/doze mode.

If the TIM 530 contains a positive indication for the STA m 506, the STAm 506 sends a PS-Poll frame 538 to the AP 502. Upon receiving thePS-Poll frame 538, the AP 502 sends a data frame 540 to the STA m 506,with the ACK indication bits set to “00.” Upon receiving the data frame540, the STA m 506 sends an ACK 542 and sets the ACK indication bits to“10.” Any non-relay STA associated to the root AP retrieves its DL dataas presently known.

In stage 2 522, the end-STA retrieves the DL data from the relay nodeusing the TIM. The relay node n 504 broadcasts a TIM 550, with onlypositive indications of end-STAs that are associated with the relay noden 504. Upon receiving a positive indication in the TIM 550, the end-STAp 508 sends a PS-Poll frame 552 in the UL to retrieve the DL data fromthe relay node n 504. Upon receiving the PS-Poll frame 552 from theend-STA p 508, the relay node n 504 sends the DL data 554 using athree-address format to the end-STA p 508 with the ACK indication bitsset to “00.” If the end-STA p 508 receives the DL data 554 correctlyfrom the relay node n 504, it sends an ACK 556 and sets the ACKindication bits to “10” for the next outgoing frame.

Similarly, upon receiving a positive indication in the TIM 550, theend-STA q 510 sends a PS-Poll frame 558 in the UL to retrieve the DLdata from the relay node n 504. Upon receiving the PS-Poll frame 558from the end-STA q 510, the relay node n 504 sends the DL data 560 usinga three-address format to the end-STA q 510 with the ACK indication bitsset to “00.” If the end-STA q 510 receives the DL data 560 correctlyfrom the relay node n 504, it sends an ACK 562 and sets the ACKindication bits to “10” for the next outgoing frame.

In this way, there is no impact on non-relay STAs, and they do not needto be aware of one or more relay nodes being used, because the time slotallocated to the relay node is the same as the time slot for thenon-relay STA.

FIG. 6 is a signal diagram of downlink data retrieval method 600 forrelay using a relay node-initiated retrieval. The method 600 isperformed between an AP 602, a relay node n 604, a STA m 606, a firstend-STA p 608, and a second end-STA q 610. The method 600 includes twostages: stage 1 620 is a relay node-initiated DL data retrieval, andstage 2 622 is an end-STA initiated DL data retrieval.

In stage 1 620, during a channel access period 630 (a time period duringwhich a device is allowed to access the channel), the relay node n 604sends a PS-Poll frame 632 in the UL to the AP 602 at any time on behalfof a set of particular end-STAs associated with the relay node n 604 (inthis capacity, the relay node n 604 functions as a R-AP). The set of theparticular end-STAs may be a specific set of end-STAs associated withthe R-AP entity within the relay node n 604. The AID/Duration field inthe PS-Poll frame 632 is set to the AID of the end-STA, which isdifferent than the TA address in the PS-Poll frame. Alternately, the setof the particular end-STAs may be all end-STAs associated with the R-APentity within the relay node n 604. The AID/Duration field in thePS-Poll frame 632 is set to a special value which represents “allend-STAs.” Alternately, the set of the particular end-STAs may be asubset of all end-STAs associated with the R-AP entity within the relaynode n 604. The AID/Duration field in the PS-Poll frame 632 may bereused to signal the subset of associated end-STAB.

Upon receiving the PS-Poll frame 632 from the relay node n 604, the AP602 sends the DL data 634 (as a MPDU for one end-STA or as an A-MPDU forseveral end-STAs) to the relay node n 604. Alternatively, the AP 602 mayreply to the PS-Poll frame 632 with an ACK frame that contains a one-bitfield with a “1” indicating that traffic is buffered (as indicated inthe TIM) and that the end-STA should stay awake (i.e., a service periodstarts) or a “0” indicating that no traffic is buffered, so the end-STAshould go back to sleep. The AP starts transmitting the DL data 634 tothe relay node n 604 after an interframe space (IFS) time (for example,a SIFS following the ACK frame.

If the relay node n 604 receives the DL data 634 for the end-STA fromthe AP 602 correctly, it sends an ACK frame 636 and sets the ACKindication bits to “10” for the next outgoing frame, which means thatthe relay node n 604 will not forward the DL data 634 to thecorresponding end-STA immediately, because it may be in a sleep/dozemode. The ACK frame 636 may be designed specifically for this purpose;for example, a short ACK frame may be used.

Alternately, the STA m 606 sends a PS-Poll frame 638 to the AP 602. Uponreceiving the PS-Poll frame 638, the AP 602 sends a data frame 640 tothe STA m 606, with the ACK indication bits set to “00.” Upon receivingthe data frame 640, the STA m 606 sends an ACK frame 642 and sets theACK indication bits to “10.” The ACK frame 642 may be designedspecifically for this purpose; for example, a short ACK frame may beused. Any non-relay STA associated to the root AP retrieves its DL dataas presently known.

In stage 2 622, the end-STA wakes up at any time to send a PS-Poll framein the UL to its associated relay node (i.e., the R-AP entity within therelay node) to retrieve the DL data from the relay node. During achannel access period 650, the end-STA p 608 sends a PS-Poll frame 652to the relay node n 604. Upon receiving the PS-Poll frame 652, the relaynode n 604 sends the DL data 654 using the three-address format to theend-STA p 608 with the ACK indication bits set to “00.” Alternatively,the relay node n 604 may reply to the PS-Poll frame 652 with an ACKframe that contains a one-bit field, with a “1” indicating that trafficis buffered (as indicated in the TIM) and the end-STA should stay awake(i.e., a service period starts), and a “0” indicating that no traffic isbuffered and the end-STA should go back to sleep. The relay node n 604starts transmitting the DL data 654 to the end-STA p 608 after an IFStime (for example, a SIFS) following the ACK frame. If the end-STA p 608receives the DL data 654 correctly from the relay node n 604, it sendsan ACK frame 656 and sets the ACK indication bits to “10” for the nextoutgoing frame.

Similarly, during the channel access period 650, the end-STA q 610 sendsa PS-Poll frame 658 to the relay node n 604. Upon receiving the PS-Pollframe 658, the relay node n 604 sends the DL data 660 using thethree-address format to the end-STA q 610 with the ACK indication bitsset to “00.” Alternatively, the relay node n 604 may reply to thePS-Poll frame 658 with an ACK frame that contains a one-bit field, witha “1” indicating that traffic is buffered (as indicated in the TIM) andthe end-STA should stay awake (i.e., a service period starts), and a “0”indicating that no traffic is buffered and the end-STA should go back tosleep. The relay node n 604 starts transmitting the DL data 660 to theend-STA q 610 after an IFS time (for example, a SIFS) following the ACKframe. If the end-STA q 610 receives the DL data 660 correctly from therelay node n 604, it sends an ACK frame 662 and sets the ACK indicationbits to “10” for the next outgoing frame.

A third method for DL data retrieval may be used (not shown in theFigures), which is a hybrid method using stage 1 520 of the method 500(the relay node retrieves the DL data from the AP on behalf of theend-STA using the TIM) and stage 2 622 of the method 600 (the end-STAinitiates DL data retrieval from the relay node).

A fourth method for DL data retrieval may be used (not shown in theFigures), which is a hybrid method using stage 1 620 of the method 600(relay initiated DL data retrieval from the AP) and stage 2 522 of themethod 500 (the end-STA retrieves the DL data from the relay node usingthe TIM).

Relay functionality may be used to serve STAs with poor link budgets.When a R-AP receives the UL data from an end-STA, it replies with anACK. When the AP receives the relayed UL data from the R-STA, it replieswith an ACK to the R-STA. However, the path through the relay node maynot always be reliable and may have temporary outages or flow/buffermanagement issues, where some data/frames will be thrown out. Toaccommodate this, there is a need to introduce a properly designed ACKand efficient flow control for receiving and transmitting frames at therelay node. In addition, the network allocation vector (NAV) settingalong the relay path needs to be carried out efficiently.

STAs that are at the edge of a BSS coverage area typically suffer poorlink quality. In addition, such STAs may also suffer from hidden nodeissues and overlapping BSS (OBSS) interference. These STAs may be servedefficiently with respect to power budget by using a relay.

A relay node is typically capable of supporting a four-address frame(i.e., transmitter, receiver, source address, and destination address)and forwarding the frame from a source node to the destination node.Typically, the relay node is aware that a frame from the source node isto be forwarded to a destination node by the destination node addressincluded in the frame when it is transmitted by the source node to therelay node.

The channel conditions from the relay node to the destination node maysometimes deteriorate. The source node is not aware of this channelcondition and may therefore keep sending frames to the relay node, whichmay cause congestion and buffer overflow at the relay node, leading topacket or frame loss. An efficient flow control mechanism is requiredwhere the relay node needs to stop accepting new frames when itsframe/packet buffer is full and try to transmit the currently bufferedframes before accepting new frames. To do this, the relay node should beable to signal to the source node to stop sending frames. This may beachieved by signaling using the “10” value for the early ACK indicationbits in the SIG field of the PHY preamble/header and using theassociated protocol and procedures described below.

When a relay node sends an ACK, BA, or any other frame to the sourcenode (AP/STA) with a “10” value for the early ACK indication bits inresponse to a frame from the source node to be forwarded to thedestination node, the source node may follow one or more of thefollowing relay flow control procedures.

(1) The source node stops sending more frames to the relay node or doesnot attempt to send more frames to the relay node.

(2) The source node does not attempt to send more data until after aspecified time.

(3) The source node does not attempt to send more data until the relaynode explicitly signals that it may do so.

(4) The source node attempts to resend the current data frame.

(5) The source node attempts to resend the current data frame after aspecified time.

(6) The source node attempts to resend the current data frame only afterthe relay node explicitly signals that it may do so.

(7) The source node may truncate the TXOP if needed, for example, with aCF-End frame.

In relay flow control in the DL (AP to STA) for a typical data/ACKsequence, the source node (AP) sends frames (e.g., data frames) to therelay node to be forwarded to the destination node. In normal relayoperation, the relay node sets a “11” value for the early ACK indicationas long as the relay node can or will forward data frames to thedestination node. So the relay node will set the early ACK indication to“11” regardless of whether the data frame has the “more data” field setto “1” (indicating that the source node has more data frames to sendafter the current data frame) or the data frame has the “more data”field set to “0” (indicating that the source node has no more dataframes to send after the current data frame).

If the relay node cannot receive more frames or equivalently cannotforward more frames, it sends a response frame, e.g., an ACK frame witha “10” value for the early ACK indication. Upon receiving an ACK framefrom the relay node with a “10” value for the early ACK indication, inresponse to a frame from the source node that should be forwarded to thedestination node, the source node (AP) may stop sending frames to therelay node for forwarding and follow the relay flow control procedures.

FIG. 7 is a signal diagram of relay flow control method 700 in the DL(AP to STA) for a data/ACK frame sequence. The method 700 is performedbetween an AP 702, a relay node 704, and a STA 706. The AP 702 sends aDL data frame 710 to the relay node 704 with the early ACK indicationbits set to “00” (step 730). Upon successful receipt of the DL dataframe 710 and after a SIFS interval 712, the relay node 704 sends an ACKframe 714 to the AP 702. The relay node 704 sets the early ACKindication bits in the ACK frame 714 to “10” to signal that the AP 702should stop sending frames (step 732). After receiving the ACK frame714, the AP 702 stops sending frames to the relay node 704 and followsthe relay flow control procedures (step 734).

The relay node 704 may access the medium to send a buffered data frame716 to the STA 706 with the early ACK indication bits set to “00” (step736). Upon successful receipt of the data frame 716 and after a SIFSinterval 718, the STA 706 sends an ACK frame 720 to the relay node 704with the early ACK indication bits set to “10” (step 738).

In one embodiment of the method 700, a short ACK may be used in place ofthe ACK.

In relay flow control in the UL (STA to AP) for a typical data/ACKsequence, the source node (STA) sends frames (e.g., data frames) to therelay node to be forwarded to the destination node. Similar to normalrelay operation for the DL, in normal relay operation in the UL, therelay node sets a “11” value for the early ACK indication as long as therelay node can or will forward data frames to the destination node. Sothe relay node will set the early ACK indication to “11” regardless ofwhether the data frame has the “more data” field set to “1” (indicatingthat the source node has more data frames to send after the current dataframe) or the data frame has the “more data” field set to “0”(indicating that the source node has no more data frames to send afterthe current data frame).

If the relay node cannot receive more frames or equivalently cannotforward more frames, it sends a response frame, e.g., an ACK frame witha “10” value for the early ACK indication. Upon receiving an ACK framefrom the relay node with a “10” value for the early ACK indication, inresponse to a frame from the source node that should be forwarded to thedestination node, the source node (STA) may stop sending frames to therelay node for forwarding and follow the relay flow control procedures.

FIG. 8 is a signal diagram of relay flow control method 800 in the UL(STA to AP) for a data/ACK frame sequence. The method 800 is performedbetween an AP 802, a relay node 804, and a STA 806. The STA 806 sends anUL data frame 810 to the relay node 804 with the early ACK indicationbits set to “00” (step 830). Upon successful receipt of the data frame810 and after a SIFS interval 812, the relay node 804 sends an ACK frame814 to the STA 806. The relay node 804 sets the early ACK indicationbits in the ACK frame 814 to “10” to signal that the STA 806 should stopsending frames (step 832). After receiving the ACK frame 814, the STA806 stops sending frames to the relay node 804 and follows the relayflow control procedures (step 834).

The relay node 804 may access the medium to send a buffered data frame816 to the AP 802 with the early ACK indication bits set to “00” (step836). Upon successful receipt of the data frame 816 and after a SIFSinterval 818, the AP 802 sends an ACK frame 820 to the relay node 804with the early ACK indication bits set to “10” (step 838).

In one embodiment of the method 800, a short ACK may be used in place ofthe ACK.

When A-MPDUs are forwarded on a relay path, it may improve theefficiency of frame transmission on the relay path because the A-MPDUcarries aggregated MPDUs. So the relay path is now accessed for theaggregated transmission of MPDUs rather than individually for eachMPDU/frame transmission. For this case, in the methods 700 and 800, thedata frame is replaced by an A-MPDU and the ACK frame is replaced by aBA frame. The A-MPDU from the source node carries a “01” value in theearly ACK indication field to signal a BA response. In the relay flowcontrol for the A-MPDU/BA sequence, the BA from the relay node carries a“10” value for the early ACK indication field to signal to the sourcenode to stop sending frames and to follow the relay flow controlprocedures.

In relay flow control for the DL (AP to STA) for a typical A-MPDU/BAsequence, if the relay node cannot receive more frames or equivalentlycannot forward more frames, it sends a response frame (e.g., a BA frame)with a “10” value for the early ACK indication. Upon receiving a BAframe from the relay node with a “10” value for the early ACKindication, in response to a frame from the source node that should beforwarded to the destination node, the source node (AP) may stop sendingframes to the relay node for forwarding and follow the relay flowcontrol procedures.

FIG. 9 is a signal diagram of relay flow control method 900 in the DLfor an A-MPDU/BA frame sequence. The method 900 is performed between anAP 902, a relay node 904, and a STA 906. The AP 902 sends a DL A-MPDUframe 910 to the relay node 904 with the early ACK indication bits setto “01” (step 930). Upon successful receipt of the A-MPDU frame 910 andafter a SIFS interval 912, the relay node 904 sends a BA frame 914 tothe AP 902. The relay node 904 sets the early ACK indication bits in theBA frame 914 to “10” to signal that the AP 902 should stop sendingframes (step 932). After receiving the BA frame 914, the AP 902 stopssending frames to the relay node 904 and follows the relay flow controlprocedures (step 934).

The relay node 904 may access the medium to send a buffered A- MPDUframe 916 to the STA 906 with the early ACK indication bits set to “01”(step 936). Upon successful receipt of the A-MPDU frame 916 and after aSIFS interval 918, the STA 906 sends a BA frame 920 to the relay node904 with the early ACK indication bits set to “10” (step 938).

In one embodiment of the method 900, a short BA may be used in place ofthe BA.

In relay flow control for the UL (STA to AP) for a typical A-MPDU/BAsequence, if the relay node cannot receive more frames or equivalentlycannot forward more frames, it sends a response frame (e.g., a BA frame)with a “10” value for the early ACK indication. Upon receiving a BAframe from the relay node with a “10” value for the early ACKindication, in response to a frame from the source node that should beforwarded to the destination node, the source node (STA) may stopsending frames to the relay node for forwarding and follow the relayflow control procedures.

FIG. 10 is a signal diagram of relay flow control method 1000 in the ULfor an A-MPDU/BA frame sequence. The method 1000 is performed between anAP 1002, a relay node 1004, and a STA 1006. The STA 1006 sends an ULA-MPDU frame 1010 to the relay node 1004 with the early ACK indicationbits set to “01” (step 1030). Upon successful receipt of the A-MPDUframe 1010 and after a SIFS interval 1012, the relay node 1004 sends aBA frame 1014 to the STA 1006. The relay node 1004 sets the early ACKindication bits in the BA frame 1014 to “10” to signal that the STA 1006should stop sending frames (step 1032). After receiving the BA frame1014, the STA 1006 stops sending frames to the relay node 1004 andfollows the relay flow control procedures (step 1034).

The relay node 1004 may access the medium to send a buffered A-MPDUframe 1016 to the AP 1002 with the early ACK indication bits set to “01”(step 1036). Upon successful receipt of the A-MPDU frame 1016 and aftera SIFS interval 1018, the AP 1002 sends a BA frame 1020 to the relaynode 1004 with the early ACK indication bits set to “10” (step 1038).

In one embodiment of the method 1000, a short BA may be used in place ofthe BA.

In one embodiment, which may be used with any other embodiment describedherein, a new short/null data packet (NDP) frame may be definedspecifically for a relay node to send to the source node to signal tothe source node to stop sending frames. Such a short/NDP frame isreferred to herein as a short/NDP relay stop frame. A short/NDP relaystop frame, sent from the relay node to the source node, may have one ormore of the following characteristics.

(1) The short/NDP relay stop frame may be sent by itself (i.e., not as aresponse frame) to prevent the source node from sending frames forforwarding.

(2) The short/NDP relay stop frame may be sent as a response to anyframe sent from the source node for forwarding to the relay node. Inthis scenario, the source node behaves as described previously for thecase when it receives a frame from the relay node with a “10” value forthe early ACK indication, in response to a frame from the source nodethat should be forwarded to the destination node.

(3) The short/NDP relay stop frame may indicate that the last frame sentby the source node earlier was not forwarded and has to be resent.

(4) The short/NDP relay stop frame may include information indicatingthat one or more frames sent by the source node earlier were notforwarded and have to be resent.

(5) The short/NDP relay stop frame may include information on a specifictime duration after which the source node may attempt to send frames forforwarding (i.e., a time out duration).

(6) The short/NDP relay stop frame may include any or all the aboveinformation in the SIG field of the PHY preamble of the frame.

FIG. 11 is a diagram of a format of a short/NDP relay stop frame 1100.The short/NDP relay stop frame 1100 includes a short training field(STF) 1102, a long training field (LTF) 1104, and a signal (SIG) field1106. The SIG field 1106 contains short/NDP relay stop information,including any one or more of: a time out duration for the source node oridentifiers for any frames that were not forwarded to the destinationnode.

In another embodiment, a new frame that is a regular frame and not ashort/NDP frame may be used in place of the short/NDP relay stop framewith the same functionality and characteristics of the short/NDP relaystop frame.

In one embodiment, which may be used with any other embodiment describedherein, a new short/NDP frame may be defined specifically for a relaynode to signal to the source node that it may attempt to start sendingframes to the relay node or that it is able to receive more frames fromthe source node. Such a short/NDP frame is referred to herein as ashort/NDP relay start frame. A short/NDP relay start frame, sent fromthe relay node to the source node, may have one or more of the followingcharacteristics.

(1) The short/NDP relay start frame may be sent by itself (i.e., not asa response frame) to signal to the source node to attempt to send framesfor forwarding.

(2) The short/NDP relay start frame may be sent as a response to a framesent from the source node requesting the frame forwarding or relayservice from the relay node.

(3) The short/NDP relay start frame may indicate that the last framesent by the source node earlier was not forwarded and has to be resent.

(4) The short/NDP relay start frame may include information indicatingthat one or more frames sent by the source node earlier were notforwarded and have to be resent.

(5) The short/NDP relay start frame may include information on aspecific time duration after which the source node may attempt to sendframes for forwarding (i.e., a time out duration).

(6) The short/NDP relay start frame may include one or more of thefollowing: the remaining buffer size at the relay node, a number offrames that may be sent by the source node, or a size of the frames thatmay be sent by the source node.

(7) The short/NDP relay start frame may include any or all the aboveinformation in the SIG field of the PHY preamble of the frame.

FIG. 12 is a diagram of a format of a short/NDP relay start frame 1200.The short/NDP relay start frame 1200 includes a STF 1202, a LTF 1204,and a SIG field 1206. The SIG field 1206 contains short/NDP relay startinformation, including any one or more of: a time out duration for thesource node, identifiers for any frames that were not forwarded to thedestination node, the remaining buffer size at the relay node, a numberof frames that may be sent by the source node, or a size of the framesthat may be sent by the source node.

In another embodiment, a new frame that is a regular frame and not ashort/NDP frame may be used in place of the short/NDP relay start framewith the same functionality and characteristics of the short/NDP relaystart frame.

One transmit opportunity (TXOP) is shared with the relay node to reducechannel access contention, but this creates the following issues. If aTXOP is reserved from the source node to the relay node and from therelay node to the destination node and includes a SIFS and an ACK time,but the relay link is bad, then one part of the entire TXOP will bewasted. The current mechanism to reserve the TXOP is primarily one-hop,and may not be directly applicable to a two-hop relay. Therefore, amechanism to reserve the TXOP from the source node to the relay node andfrom the relay node to the destination node is needed, and a method totruncate the relay-shared TXOP when the relay link goes bad is desired.

To facilitate the ready to send (RTS)/clear to send (CTS) based TXOPreservation for a two-hop based relay, a frame format for a relay-RTS(R-RTS) frame is described. The R-RTS frame may reuse the frame formatof the existing RTS frame including the modifications described herein.

R-RTS format 1: The R-RTS frame includes a PLCP header and a MAC headerwhich contains Frame Control, Duration, TA, receiver address (RA), andframe check sequence (FCS) fields. A one-bit field in the SIG field ofthe PLCP header is reused to indicate whether the R-RTS frame is used toreserve the TXOP for relay or the time duration by which if thePHY_RXSTART.indication primitive is not received, then a STA that usedinformation from an RTS/R-RTS frame as the most recent basis to updateits NAV is permitted to reset its NAV to be larger than the normalRTS/CTS case.

R-RTS format 2: The R-RTS frame includes a PLCP header and a MAC headerwhich contains Frame Control, Duration, TA, RA, and FCS fields.Additionally, the MAC header contains a new one-bit indication whichsignals whether the R-RTS frame is used to reserve the TXOP for relay orthe time duration by which if the PHY-RXSTART.indication primitive isnot detected, then a STA that used information from an RTS/R-RTS frameas the most recent basis to update its NAV setting is permitted to resetits NAV is larger than the normal RTS/CTS case.

In both formats 1 and 2, if the one-bit indication (in the SIG field orin the MAC header) is set to “1”, it implies the same information. A STAthat used information from an RTS/R-RTS frame as the most recent basisto update its NAV setting is permitted to reset its NAV if noPHY-RXSTART.indication primitive is detected from the PHY during aperiod with a duration of:

(4×aSIFSTime)+(2×CTS_Time)+(R-RTS_Time)+aPHY-RX-START-Delay+(4×aSlotTime)  Equation (2)

This period starts at the PHY-RXEND.indication primitive correspondingto the detection of the RTS/R-RTS frame if the relay node transmits aR-RTS frame in the two-hop relay TXOP reservation procedure (describedbelow) is implemented. Alternatively, if the relay node transmits a CTSframe in the two-hop relay TXOP reservation procedure (described below)is implemented, the effective period is:

(5×aSIFSTime)+(3×CTS_Time)+(R-RTS_Time)+aPHY-RX-START-Delay+(5×aSlotTime)  Equation (3)

If the one-bit indication is set to “0,” it implies that a STA that usedinformation from an RTS/R-RTS frame as the most recent basis to updateits NAV setting is permitted to reset its NAV if noPHY-RXSTART.indication primitive is detected from the PHY during aperiod with a duration of:

(2×aSIFSTime)+(CTS_Time)+aPHY-RX-START-Delay+(2×aSlotTime)   Equation(4)

This period starts at the PHY-RXEND.indication primitive correspondingto the detection of the RTS/R-RTS frame.

FIG. 13 is a signal diagram of a network allocation vector (NAV) settingmethod 1300 for relay in a case of a successful data transmission. Themethod 1300 is performed between a source node 1302, a relay node 1304,a destination node 1306, and other STAs 1308.

The source node 1302 initiates the TXOP reservation procedures for theentire duration of the relay frame exchanges, and the duration totransmit the data frame from the relay node to the destination node isassumed to be the worst case or calculated conservatively.

The source node 1302 sends a R-RTS frame 1310 with the one-bitindication set to “1” to the relay node 1304. The duration field in theR-RTS frame 1310 depends on the detailed signaling procedures.

If the relay node 1304 sends a R-RTS frame (described below), theduration is:

7×aSIFS time+2×CTS_Time+R-RTS_Time+2×ACK_time+Data_Time(source node torelay node)+Data_Time(relay node to destination node)   Equation (5)

If the relay node 1304 sends a CTS frame (described below), the durationis:

8×aSIFS time+3×CTS_Time+R-RTS_Time+2×ACK_time+Data_Time(source node torelay node)+Data_Time (relay node to destination node)   Equation (6)

The Data_Time value (source node to relay node) in Equations (5) and (6)is calculated using the length of the data frame and data rate used forthe transmission. The Data_Time value (relay node to destination node)in Equations (5) and (6) is calculated using the length of the dataframe and the assumption that the lowest data rate is used for thetransmission between the relay node and the destination node. If thesource node has knowledge of link between the relay node and thedestination node through channel feedback or other means, it calculatesthe Data_Time value (relay node to destination node) conservativelyusing the length of the data frame and a lower bound of the data rate tobe used for the transmission between the relay node and the destinationnode.

Any of the other STAs 1308 that receive the R-RTS frame 1310 set theirNAV based on the duration field value of the R-RTS frame 1310 (step1350).

There are two possible procedures for a relay node 1304 that receivesthe R-RTS frame 1310. In one procedure, the relay node 1304 transmits aR-RTS frame 1312 with the one-bit indication set to “0” to thedestination node 1306 after a SIFS interval 1314 if the NAV at the relaynode 1304 indicates that the medium is idle. The duration field of theR-RTS frame 1312 is the value obtained from the duration field of theR-RTS frame 1310 received from the source node 1302, minus the time inmicroseconds required to transmit the R-RTS frame 1310 and the SIFSinterval 1314. The RA field is set as the MAC address of the destinationnode 1306, and the TA field is set as the MAC address of the relay node1304. The R-RTS frame 1312 may also serve as an implicit CTS to theR-RTS frame 1310 from the source node 1302. Upon receiving/detecting theR-RTS frame 1312 from the relay node 1304, the source node 1302 maydetermine whether its R-RTS frame 1310 transmission succeeds or not byone of the following.

(1) The source node 1302 checks whether the TA field of the R-RTS frame1312 matches the RA field of the R-RTS frame 1310 transmitted by thesource node 1302.

(2) If the source node 1302 knows the MAC address of the destinationnode 1306, it checks whether the RA field of the R-RTS frame 1312matches the MAC address of the destination node 1306.

(3) If the source node 1302 knows the MAC address of the destinationnode 1306, it checks whether the TA field of the R-RTS frame 1312matches the RA field of the R-RTS frame 1310 transmitted by the sourcenode 1302 and whether the RA field of the R-RTS frame 1312 matches theMAC address of the destination node 1306.

The same rule of CTS reception within the CTSTimeout interval for thesource node (as described in connection with the second procedure below)applies to the implicit CTS (i.e., the R-RTS from the relay node 1304)as well.

In a second procedure (not shown in FIG. 13), the relay node 1304 thatis addressed by the R-RTS frame 1310 transmits an explicit CTS frame tothe source node 1302 after the SIFS interval 1314 if the NAV at therelay node 1304 indicates that the medium is idle. The RA field of theCTS frame is copied from the TA field of the R-RTS frame 1310. Theduration field of the CTS field is the value obtained from the durationfield of the R-RTS frame 1310, minus the time in microseconds requiredto transmit the CTS frame and the SIFS interval 1314.

If the source node 1302 does not receive such an explicit CTS frame fromthe relay node 1304 within a CTSTimeout interval, with a value ofaSIFSTime+aSlotTime+aPHY-RX-START-Delay, starting at thePHY-TXEND.confirm primitive, then the source node 1302 concludes thatthe transmission of the R-RTS frame 1310 has failed and invokes itsbackoff procedure upon expiration of the CTSTimeout interval. If such anexplicit CTS frame from the relay node 1304 is received during theCTSTimeout interval, the source node 1302 concludes that thetransmission of the R-RTS frame 1310 succeeded, but holds its datatransmission.

Then, the relay node 1304 sends the R-RTS frame 1312 with the one-bitindication set to “0” to the destination node 1306 after a SIFS intervalafter sending the CTS. The duration field of the R-RTS frame 1312 is thevalue obtained from the duration field of the CTS frame from the relaynode 1304 to the source node 1302, minus the time in microsecondsrequired to transmit the R-RTS frame 1310 and its SIFS interval 1314.The RA field is set as the MAC address of the destination node 1306, andthe TA field is set as the MAC address of the relay node 1304.

Any of the other STAs 1308 that receive the R-RTS frame 1312 set theirNAV based on the duration field value of the R-RTS frame 1312 (step1352).

The destination node 1306 that is addressed by the R-RTS frame 1312 fromthe relay node 1304 transmits a CTS frame 1316 to the relay node 1304after a SIFS interval 1318 if the NAV at the destination node 1306indicates that the medium is idle. The field setting of the CTS frame1316 in reference to the R-RTS frame 1312 and the rule of handling theCTSTimeout is the same as currently implemented.

Any of the other STAs 1308 that receive the CTS frame 1316 set their NAVbased on the duration field value of the CTS frame 1316 (step 1354).

Upon receiving the CTS frame 1316 from the destination node 1306 withinthe CTSTimeout interval, the relay node 1304 transmits a CTS frame 1320addressed to the source node 1302 to indicate whether the TXOPreservation for the two-hop relay succeeds. Different than conventionalCTS transmission, at this step the relay node 1304 does need to check ifthe NAV at the relay node indicates that the medium is idle, because theprevious steps have guaranteed that the medium is idle. The RA field ofthe CTS frame 1320 is set to the MAC address of the source node 1302.The duration field of the CTS frame 1320 is the value obtained from theduration field of the CTS frame 1316, minus the time in microsecondsrequired to transmit the CTS frame 1316 and its SIFS interval 1322.

Any of the other STAs 1308 that receive the CTS frame 1320 set their NAVbased on the duration field value of the CTS frame 1320 (step 1356).

Upon receiving the CTS frame 1320 from the relay node 1304, the sourcenode 1302 knows that the TXOP reservation for the two-hop relaysucceeds. The source node 1302 starts transmitting a data frame 1324after a SIFS interval 1326 following the CTS frame 1320 received fromthe relay node 1304.

The relay node 1304 processes the received data frame 1324. If thereceived data frame 1324 is decoded correctly, the relay node 1304 sendsan ACK frame 1328 after a SIFS interval 1330 without changing theduration of reserved TXOP.

If the received data frame 1324 is not decoded correctly, the sourcenode 1302 will not receive an ACK by the time aSIFS time+ACK_Time aftersending the data frame 1324. The source node 1302 will release the TXOPby sending a CF-End frame 1332. The relay node 1304 sends a CF-End frame1334 and the destination node 1306 sends a CF-End frame 1336 uponreceipt of the CF-End frame 1332.

If the relay node 1304 successfully receives the data frame 1324, therelay node 1304 transmits the data frame as data frame 1338 to thedestination node 1306 after a SIFS interval 1340. The destination node1306 processes the received data frame 1338 from the relay node 1304. Ifreceived data frame 1338 is decoded correctly, the destination node 1306sends an ACK frame 1342 after a SIFS interval 1344. The destination node1306 may use a method at this step to release the TXOP and reset the NAVfor the other STAs 1308 near the destination node 1306. For example, thedestination node 1306 may set the ACK indication to be “10” in theoutgoing frame.

Upon receiving the ACK frame 1342 from the destination node 1306 and ifthe current TXOP has not yet expired, the relay node 1304 sends theCF-End frame 1334 after a SIFS interval 1346 to truncate/release theTXOP. If the relay node 1304 does not receive the ACK frame 1342 withinaSIFS time+ACK_Time after sending the data frame 1338 and the remainingTXOP allows it to retransmit the data frame 1338, it may retransmit thedata frame 1338 to the destination node 1306.

Upon receiving the CF-End frame 1334 from the relay node 1304 before thecurrent TXOP expires, the source node 1302 sends the CF-End frame 1332after a SIFS interval 1348.

Upon receiving the CF-End frame 1334 from the relay node 1304 before thecurrent TXOP expires, the destination node 1306 sends the CF-End frame1336. This step is only necessary if the method to release TXOP andreset the NAV has not been previously applied. There is no need toimplement both steps.

When the TXOP is released, the NAV at the other STAs 1308 is reset (step1358).

FIG. 14 is a signal diagram of a second NAV setting method 1400 forrelay in a case of a successful data transmission. The method 1400 isperformed between a source node 1402, a relay node 1404, a destinationnode 1406, and other STAs 1408.

The source node 1402 initiates the TXOP reservation procedures for theentire duration of the relay frame exchanges, and the duration totransmit the data frame from the relay node to the destination node isassumed to be the worst case or calculated conservatively.

The source node 1402 sends a R-RTS frame 1410 with the one-bitindication set to “1” to the relay node 1404. The duration field in theR-RTS frame 1410 depends on the detailed signaling procedures.

If the relay node 1404 sends a R-RTS frame (described below), theduration is:

7×aSIFS time+2×CTS_Time+R-RTS_Time+2×ACK_time+Data_Time(source node torelay node)+Data_Time (relay node to destination node)   Equation (7)

If the relay node 1404 sends a CTS frame (described below), the durationis:

8×aSIFS time+3×CTS_Time+R-RTS_Time+2×ACK_time+Data_Time(source node torelay node)+Data_Time (relay node to destination node)   Equation (8)

The Data_Time value (source node to relay node) in Equations (7) and (8)is calculated using the length of the data frame and data rate used forthe transmission. The Data_Time value (relay node to destination node)in Equations (7) and (8) is calculated using the length of the dataframe and the assumption that the lowest data rate is used for thetransmission between the relay node and the destination node. If thesource node has knowledge of link between the relay node and thedestination node through channel feedback or other means, it calculatesthe Data_Time value (relay node to destination node) conservativelyusing the length of the data frame and a lower bound of the data rate tobe used for the transmission between the relay node and the destinationnode.

Any of the other STAs 1408 that receive the R-RTS frame 1410 set theirNAV based on the duration field value of the R-RTS frame 1410 (step1450).

There are two possible procedures for a relay node 1404 that receivesthe R-RTS frame 1410. In one procedure, the relay node 1404 transmits aR-RTS frame 1412 with the one-bit indication set to “0” to thedestination node 1406 after a SIFS interval 1414 if the NAV at the relaynode 1404 indicates that the medium is idle. The duration field of theR-RTS frame 1412 is the value obtained from the duration field of theR-RTS frame 1410 received from the source node 1402, minus the time inmicroseconds required to transmit the R-RTS frame 1410 and the SIFSinterval 1414. The RA field is set as the MAC address of the destinationnode 1406, and the TA field is set as the MAC address of the relay node1404. The R-RTS frame 1412 may also serve as an implicit CTS to theR-RTS frame 1410 from the source node 1402. Upon receiving/detecting theR-RTS frame 1412 from the relay node 1404, the source node 1402 maydetermine whether its R-RTS frame 1410 transmission succeeds or not byone of the following.

(1) The source node 1402 checks whether the TA field of the R-RTS frame1412 matches the RA field of the R-RTS frame 1410 transmitted by thesource node 1402.

(2) If the source node 1402 knows the MAC address of the destinationnode 1406, it checks whether the RA field of the R-RTS frame 1412matches the MAC address of the destination node 1406.

(3) If the source node 1402 knows the MAC address of the destinationnode 1406, it checks whether the TA field of the R-RTS frame 1412matches the RA field of the R-RTS frame 1410 transmitted by the sourcenode 1402 and whether the RA field of the R-RTS frame 1412 matches theMAC address of the destination node 1406.

The same rule of CTS reception within the CTSTimeout interval for thesource node (as described in connection with the second procedure below)applies to the implicit CTS (i.e., the R-RTS from the relay node 1404)as well.

In a second procedure (not shown in FIG. 14), the relay node 1404 thatis addressed by the R-RTS frame 1410 transmits an explicit CTS frame tothe source node 1402 after the SIFS interval 1414 if the NAV at therelay node 1404 indicates that the medium is idle. The RA field of theCTS frame is copied from the TA field of the R-RTS frame 1410. Theduration field of the CTS field is the value obtained from the durationfield of the R-RTS frame 1410, minus the time in microseconds requiredto transmit the CTS frame and the SIFS interval 1414.

If the source node 1402 does not receive such an explicit CTS frame fromthe relay node 1404 within a CTSTimeout interval, with a value ofaSIFSTime+aSlotTime+aPHY-RX-START-Delay, starting at thePHY-TXEND.confirm primitive, then the source node 1402 concludes thatthe transmission of the R-RTS frame 1410 has failed and invokes itsbackoff procedure upon expiration of the CTSTimeout interval. If such anexplicit CTS frame from the relay node 1404 is received during theCTSTimeout interval, the source node 1402 concludes that thetransmission of the R-RTS frame 1410 succeeded, but holds its datatransmission.

Then, the relay node 1404 sends the R-RTS frame 1412 with the one- bitindication set to “0” to the destination node 1406 after a SIFS intervalafter sending the CTS. The duration field of the R-RTS frame 1412 is thevalue obtained from the duration field of the CTS frame from the relaynode 1404 to the source node 1402, minus the time in microsecondsrequired to transmit the R-RTS frame 1410 and its SIFS interval 1414.The RA field is set as the MAC address of the destination node 1406, andthe TA field is set as the MAC address of the relay node 1404.

Any of the other STAs 1408 that receive the R-RTS frame 1412 set theirNAV based on the duration field value of the R-RTS frame 1412 (step1452).

The destination node 1406 that is addressed by the R-RTS frame 1412 fromthe relay node 1404 transmits a CTS frame 1416 to the relay node 1404after a SIFS interval 1418 if the NAV at the destination node 1406indicates that the medium is idle. The field setting of the CTS frame1416 in reference to the R-RTS frame 1412 and the rule of handling theCTSTimeout is the same as currently implemented.

Any of the other STAs 1408 that receive the CTS frame 1416 set their NAVbased on the duration field value of the CTS frame 1416 (step 1454).

Upon receiving the CTS frame 1416 from the destination node 1406 withinthe CTSTimeout interval, the relay node 1404 transmits a CTS frame 1420addressed to the source node 1402 to indicate whether the TXOPreservation for the two-hop relay succeeds. Different than conventionalCTS transmission, at this step the relay node 1404 does need to check ifthe NAV at the relay node indicates that the medium is idle, because theprevious steps have guaranteed that the medium is idle. The RA field ofthe CTS frame 1420 is set to the MAC address of the source node 1402.The duration field of the CTS frame 1420 is the value obtained from theduration field of the CTS frame 1416, minus the time in microsecondsrequired to transmit the CTS frame 1416 and its SIFS interval 1422.

Any of the other STAs 1408 that receive the CTS frame 1420 set their NAVbased on the duration field value of the CTS frame 1420 (step 1456).

Upon receiving the CTS frame 1420 from the relay node 1404, the sourcenode 1402 knows that the TXOP reservation for the two-hop relaysucceeds. The source node 1402 starts transmitting a data frame 1424after a SIFS interval 1426 following the CTS frame 1420 received fromthe relay node 1404.

The relay node 1404 processes the received data frame 1424. If thereceived data frame 1424 is decoded correctly, the relay node 1404 sendsan ACK frame 1428 after a SIFS interval 1430, with the ACK indicationbits set to “11.” At this point, the relay node 1404 has a goodknowledge of the duration to transmit the data frame to the destinationnode 1406. The duration of the remaining TXOP is set to be:

2×aSIFS time+Data_Time (relay node to destination node)+ACK_time  Equation (9)

The Data_Time value (relay node to destination node) is calculated usingthe length of the data frame and the data rate used for the transmissionfrom the relay node 1404 to the destination node 1406.

Any of the other STAs 1408 that receive the ACK frame 1428 set their NAVbased on the duration field value of the ACK frame 1428 (step 1458).

If the received data frame 1424 is not decoded correctly, the sourcenode 1402 will not receive an ACK by the time aSIFS time+ACK_Time aftersending the data frame 1424. The source node 1402 releases the TXOP bysending a CF-End frame 1432 or retransmits the data frame 1424 to therelay node 1404. If the source node 1402 releases the TXOP, then therelay node 1404 sends a CF-End frame (not shown in FIG. 14) and thedestination node 1406 sends a CF-End frame (not shown in FIG. 14) uponreceipt of the CF-End frame 1432.

If the relay node 1404 successfully receives the data frame 1424, therelay node 1404 transmit the data frame as data frame 1434 to thedestination node 1406 after a SIFS interval 1436. The destination node1406 processes the received data frame 1434 from the relay node 1404. Ifthe received data frame 1434 is decoded correctly, the destination node1406 sends an ACK frame 1438 after a SIFS interval 1440. The destinationnode 1406 may use a method at this step to release the TXOP and resetthe NAV for the other STAs 1408 near the destination node 1406. Forexample, the destination node 1406 may set the ACK indication bits to“10” in the outgoing frame.

After a SIFS interval 1442 by the end of TXOP set by the ACK frame 1428from the relay node 1404, the source node 1402 sends the CF-End frame1432. When the TXOP is released, the NAV at the other STAs 1408 is reset(step 1460).

Alternatively, a “Data+CF-ACK” frame may be used to carry both the dataframe from the relay node to the destination node and the ACK for thedata transmitted from the source node to the relay node. Such a framemay be a new defined frame or a reused existing Data+CF-ACK frame. Theimplicit ACK method may be considered a special case of using only oneframe to carry both the data frame from the relay node to thedestination node and the ACK for the data frame transmitted from thesource node to the relay node. When one frame transmitted by the relaynode carries both the data frame from the relay node to the destinationnode and the ACK for the data transmitted from the source node to therelay node, the timing of the procedures in both methods 1300 and 1400are reduced by the ACK_Time and a SIFS time, as shown in connection witha method 1500 shown in FIG. 15 and described below. For example, theduration of the R-RTS frame from the source node to the relay nodeincludes:

6×aSIFS time+2×CTS_Time+R-RTS_Time+ACK_time+Data_Time(source node torelay node)+Data_Time (relay node to destination node)   Equation (10)

FIG. 15 is a signal diagram of a third NAV setting method 1500 for relayin a case of a successful data transmission. The method 1500 isperformed between a source node 1502, a relay node 1504, a destinationnode 1506, and other STAs 1508.

The source node 1502 initiates the TXOP reservation procedures for theentire duration of the relay frame exchanges, and the duration totransmit the data frame from the relay node to the destination node isassumed to be the worst case or calculated conservatively.

The source node 1502 sends a R-RTS frame 1510 with the one-bitindication set to “1” to the relay node 1504. The duration field in theR-RTS frame 1510 depends on the detailed signaling procedures.

If the relay node 1504 sends a R-RTS frame (described below), theduration is:

7×aSIFS time+2×CTS_Time+R-RTS_Time+2×ACK_time+Data_Time(source node torelay node)+Data_Time (relay node to destination node)   Equation (11)

If the relay node 1504 sends a CTS frame (described below), the durationis:

8×aSIFS time+3×CTS_Time+R-RTS_Time+2×ACK_time+Data_Time(source node torelay node)+Data_Time (relay node to destination node)   Equation (12)

The Data_Time value (source node to relay node) in Equations (11) and(12) is calculated using the length of the data frame and data rate usedfor the transmission. The Data_Time value (relay node to destinationnode) in Equations (11) and (12) is calculated using the length of thedata frame and the assumption that the lowest data rate is used for thetransmission between the relay node and the destination node. If thesource node has knowledge of link between the relay node and thedestination node through channel feedback or other means, it calculatesthe Data_Time value (relay node to destination node) conservativelyusing the length of the data frame and a lower bound of the data rate tobe used for the transmission between the relay node and the destinationnode.

Any of the other STAs 1508 that receive the R-RTS frame 1510 set theirNAV based on the duration field value of the R-RTS frame 1510 (step1550).

There are two possible procedures for a relay node 1504 that receivesthe R-RTS frame 1510. In one procedure, the relay node 1504 transmits aR-RTS frame 1512 with the one-bit indication set to “0” to thedestination node 1506 after a SIFS interval 1514 if the NAV at the relaynode 1504 indicates that the medium is idle. The duration field of theR-RTS frame 1512 is the value obtained from the duration field of theR-RTS frame 1510 received from the source node 1502, minus the time inmicroseconds required to transmit the R-RTS frame 1510 and the SIFSinterval 1514. The RA field is set as the MAC address of the destinationnode 1506, and the TA field is set as the MAC address of the relay node1504. The R-RTS frame 1512 may also serve as an implicit CTS to theR-RTS frame 1510 from the source node 1502. Upon receiving/detecting theR-RTS frame 1512 from the relay node 1504, the source node 1502 maydetermine whether its R-RTS frame 1510 transmission succeeds or not byone of the following.

(1) The source node 1502 checks whether the TA field of the R-RTS frame1512 matches the RA field of the R-RTS frame 1510 transmitted by thesource node 1502.

(2) If the source node 1502 knows the MAC address of the destinationnode 1506, it checks whether the RA field of the R-RTS frame 1512matches the MAC address of the destination node 1506.

(3) If the source node 1502 knows the MAC address of the destinationnode 1506, it checks whether the TA field of the R-RTS frame 1512matches the RA field of the R-RTS frame 1510 transmitted by the sourcenode 1502 and whether the RA field of the R-RTS frame 1512 matches theMAC address of the destination node 1506.

The same rule of CTS reception within the CTSTimeout interval for thesource node (as described in connection with the second procedure below)applies to the implicit CTS (i.e., the R-RTS from the relay node 1504)as well.

In a second procedure (not shown in FIG. 15), the relay node 1504 thatis addressed by the R-RTS frame 1510 transmits an explicit CTS frame tothe source node 1502 after the SIFS interval 1514 if the NAV at therelay node 1504 indicates that the medium is idle. The RA field of theCTS frame is copied from the TA field of the R-RTS frame 1510. Theduration field of the CTS field is the value obtained from the durationfield of the R-RTS frame 1510, minus the time in microseconds requiredto transmit the CTS frame and the SIFS interval 1514.

If the source node 1502 does not receive such an explicit CTS frame fromthe relay node 1504 within a CTSTimeout interval, with a value ofaSIFSTime+aSlotTime+aPHY-RX-START-Delay, starting at thePHY-TXEND.confirm primitive, then the source node 1502 concludes thatthe transmission of the R-RTS frame 1510 has failed and invokes itsbackoff procedure upon expiration of the CTSTimeout interval. If such anexplicit CTS frame from the relay node 1504 is received during theCTSTimeout interval, the source node 1502 concludes that thetransmission of the R-RTS frame 1510 succeeded, but holds its datatransmission.

Then, the relay node 1504 sends the R-RTS frame 1512 with the one-bitindication set to “0” to the destination node 1506 after a SIFS intervalafter sending the CTS. The duration field of the R-RTS frame 1512 is thevalue obtained from the duration field of the CTS frame from the relaynode 1504 to the source node 1502, minus the time in microsecondsrequired to transmit the R-RTS frame 1510 and its SIFS interval 1514.The RA field is set as the MAC address of the destination node 1506, andthe TA field is set as the MAC address of the relay node 1504.

Any of the other STAs 1508 that receive the R-RTS frame 1512 set theirNAV based on the duration field value of the R-RTS frame 1512 (step1552).

The destination node 1506 that is addressed by the R-RTS frame 1512 fromthe relay node 1504 transmits a CTS frame 1516 to the relay node 1504after a SIFS interval 1518 if the NAV at the destination node 1506indicates that the medium is idle. The field setting of the CTS frame1516 in reference to the R-RTS frame 1512 and the rule of handling theCTSTimeout is the same as currently implemented.

Any of the other STAs 1508 that receive the CTS frame 1516 set their NAVbased on the duration field value of the CTS frame 1516 (step 1554).

Upon receiving the CTS frame 1516 from the destination node 1506 withinthe CTSTimeout interval, the relay node 1504 transmits a CTS frame 1520addressed to the source node 1502 to indicate whether the TXOPreservation for the two-hop relay succeeds. Different than conventionalCTS transmission, at this step the relay node 1504 does need to check ifthe NAV at the relay node indicates that the medium is idle, because theprevious steps have guaranteed that the medium is idle. The RA field ofthe CTS frame 1520 is set to the MAC address of the source node 1502.The duration field of the CTS frame 1520 is the value obtained from theduration field of the CTS frame 1516, minus the time in microsecondsrequired to transmit the CTS frame 1516 and its SIFS interval 1522.

Any of the other STAs 1508 that receive the CTS frame 1520 set their NAVbased on the duration field value of the CTS frame 1520 (step 1556).

Upon receiving the CTS frame 1520 from the relay node 1504, the sourcenode 1502 knows that the TXOP reservation for the two-hop relaysucceeds. The source node 1502 starts transmitting a data frame 1524after a SIFS interval 1526 following the CTS frame 1520 received fromthe relay node 1504.

The relay node 1504 processes the received data frame 1524. If thereceived data frame 1524 is decoded correctly, the relay node 1504forwards the data frame to the destination node 1506 by sending aData+CF-ACK frame 1528 after a SIFS interval 1530, with a NAV setting inits MAC header whose duration is calculated using the length of the dataframe and the data rate used for the transmission.

If the received data frame 1524 is not decoded correctly, the sourcenode 1502 will not receive an ACK by the time aSIFS time +ACK_Time aftersending the data frame 1524. The source node 1502 releases the TXOP bysending a CF-End frame 1532. If the source node 1502 releases the TXOP,then the relay node 1504 sends a CF-End frame (not shown in FIG. 15) andthe destination node 1506 sends a CF-End frame (not shown in FIG. 15)upon receipt of the CF-End frame 1532.

The destination node 1506 processes the received data frame (from thereceived Data+CF-ACK frame 1528) from the relay node 1504. If thereceived data frame is decoded correctly, the destination node 1506sends an ACK frame 1534 after a SIFS interval 1536. The destination node1506 may use a method at this step to release the TXOP and reset the NAVfor the other STAs 1508 near the destination node 1506. For example, thedestination node 1506 may set the ACK indication bits to “10” in theoutgoing frame.

Upon receiving the Data+CF-ACK frame 1528 from the relay node 1504before the current TXOP expires, the source node 1502 sends the CF-Endframe 1532 after a SIFS interval 1538 following the duration signaled inthe NAV setting in the received Data+CF-ACK frame 1528.

FIG. 16 is a signal diagram of a fourth NAV setting method 1600 forrelay in a case of a successful data transmission. The method 1600 isperformed between a source node 1602, a relay node 1604, a destinationnode 1606, and other STAs 1608.

The source node 1602 reserves the TXOP for the duration of the frameexchanges between the source node 1602 and the relay node 1604. Thesource node sends an RTS frame 1610 to the relay node 1604. The durationin the RTS frame 1610 includes:

3×aSIFS time+CTS_Time+ACK_time+Data_Time(source node to relay node)  Equation (13)

The Data_Time value (source node to relay node) in Equation (13) iscalculated using the length of the data frame and the data rate used forthe transmission. Any of the other STAs 1608 that receive the RTS frame1610 set their NAV based on the duration field value of the RTS frame1610 (step 1640).

After receiving the RTS frame 1610, the relay node 1604 waits for a SIFSinterval 1612 and transmits a CTS frame 1614 to the source node 1602.Any of the other STAs 1608 that receive the CTS frame 1614 set their NAVbased on the duration field value of the CTS frame 1614 (step 1642).

Upon receipt of the CTS frame 1614, the source node 1602 transmits adata frame 1616 after a SIFS interval 1618. The relay node 1604processes the received data frame 1616. If the received data frame 1616is decoded correctly, the relay node 1604 sends an ACK frame 1620 aftera SIFS interval 1622, and sets the ACK indication bits to “11” in thenext outgoing frame. The duration field in the ACK frame 1620 is set tothe value of:

3×aSIFSTime+CTS-to-self_Time(at destinationnode)+ACK_time+Data_Time(relay node to destination node)   Equation (14)

or

4×aSIFSTime+CTS-to-self_Time(at source node)+CTS-to-self_Time(atdestination node)+ACK_time+Data_Time(relay node to destination node)  Equation (15)

The choice between using Equation (14) or Equation (15) to determine theduration field depends on whether the optional CTS-to-self frame at thesource node 1602 is implemented or not, as will be described below. Ifthe source node implements the optional CTS-to-self frame, then Equation(15) is used to determine the duration field. The Data_Time value (relaynode to destination node) in Equations (14) and (15) is calculated usingthe length of the data frame and the data rate used for the transmissionfrom the relay node 1604 to the destination node 1606.

Any of the other STAs 1608 that receive the ACK frame 1620 set their NAVbased on the duration field value of the ACK frame 1620 (step 1644).

If the received data frame 1616 is not decoded correctly, the sourcenode 1602 will not receive an ACK by the time aSIFS time+ACK_Time aftersending the data frame 1616. The TXOP then ends.

Upon receiving the ACK frame 1620 from the relay node 1604, thedestination node 1606 sends a CTS-to-self frame 1624 after a SIFSinterval 1626, with the end of the TXOP aligned with the end of the TXOPset above by the relay node, if the NAV at the destination node 1606indicates that the medium is idle. Any of the other STAs 1608 thatreceive the CTS-to-self frame 1624 set their NAV based on the durationfield value of the CTS-to-self frame 1624 (step 1646).

Optionally, the source node 1602 may send a CTS-to-self frame 1628 aftera SIFS interval 1630, with the end of TXOP aligned with the end of theTXOP set above by the relay node. Any of the other STAs 1608 thatreceive the CTS-to-self frame 1628 set their NAV based on the durationfield value of the CTS-to-self frame 1628 (step 1648).

After the SIFS interval 1630 following the CTS-to-self frame 1624 fromthe destination node 1606 or a SIFS interval 1632 if the optionalCTS-to-self frame 1628 from the source node 1602, the relay node 1604transmits the data frame as a data frame 1634 to the destination node1606. The destination node 1606 processes the received data frame 1634.If the received data frame 1634 is decoded correctly, the destinationnode 1606 sends an ACK frame 1636 to the relay node 1604 after a SIFSinterval 1638. The destination node 1606 may set the ACK indication bitsto “10” in the outgoing frame.

After the ACK frame 1636 is sent, this indicates the end of the frameexchange sequence. The other STAs 1608 wait for an interframe space1650, which may be a SIFS, a point coordination function interframespace (PIFS), or a distributed coordination function interframe space(DIFS) before entering a back-off window 1652.

The current UL frame delivery procedure allows the AP to assign achannel access slot to the STA to contend using a management frame whenrequested by the STA. When using relay functions, the R-AP does not havefull knowledge of the usage of all channel access slots as the AP doeswhen requested by an end-STA. Without appropriate coordination betweenthe AP and the R-AP and consideration of the limited range of meters andsensors operating on lower power, either an overload or anunder-utilization of some channel access slots may happen.

Currently, the TIM is carried on a beacon. The relay node may broadcastits beacon with the full TIM, the same as broadcast by the root AP.However, this is inefficient when using relay because only a smallnumber of end- STAs are actually associated with the relay node.Therefore, methods to reduce the overhead for the TIM broadcast by therelay node are desirable.

The TIM indication and data retrieval procedures for end-STAs that areassociated with R-APs are as follows. For a R-AP, when it becomes arelay node for a root STA, it may be assigned two AIDs. One AID is forthe R-STA, which may represent the STA itself, in case the STA itselfmay also transmit and receive data traffic. A second AID is for theR-AP, which may represent the group of end-STAs that are associated withthe R-AP. Alternatively, the group of end-STAs that are associated withthe R-AP may also be identified by a group identifier.

When one or more end-STAs choose to associate with a R-AP instead of theroot AP, the R-AP may report the new association to the root AP using anend-STA Report Information Element (IE), for example, as shown in FIG.17. The end-STA Report IE may be used in connection with any of theembodiments described herein.

The end-STA Report IE 1700 includes an element ID field 1702, a lengthfield 1704, a number of fields indication 1706, and a plurality ofinformation fields 1708 a-1708 n. The element ID field 1702 includes anidentifier indicating that it is an end-STA Report IE. The length field1704 indicates the length of the end-STA Report IE 1700. The number offields indication 1706 includes the number of end-STAs reported in theIE 1700. Each information field 1708 a-1708 n contains the informationof one end-STA, including an ID subfield 1710, a previous associationsubfield 1712, and a previous AID subfield 1714.

The ID subfield 1710 includes the ID of the end-STA, which may beimplemented as a MAC address, an AID, or any other type of IDs that theSTAs and the AP have agreed upon. The previous association subfield 1712indicates the previous association of the end-STA and may be implementedas the MAC address of the previous AP, R-AP, or root AP that the end-STAwas associated with. The previous AID subfield 1714 includes the AID ofthe root AP that the end-STA was previously associated with, if any.

The end-STA Report IE 1700 or any subset of the fields or subfieldsthereof may be implemented as a field, a subfield, or subsets ofsubfields of any existing or new IE; as a part of any control,management, or other type of frame; or in MAC/PLCP headers.

The R-AP may assign another AID value to the end-STA that is associatedwith the R-AP. The TIM indications for the end-STAs in beacons from theR-AP may follow this new AID assignment.

When the root AP receives the end-STA Report IE 1700, it associates theMAC address/ID of the end-STA with the AID or MAC address of the R-APand acknowledges receipt of the end-STA Report IE 1700 using an ACK, aBA, or other type of frame.

The AP may assign two separate UL time slots of different length(following the same TIM beacon or TIM short beacon, or following twodifferent TIM beacons or TIM short beacons) for the two different AIDsin the same or different RAW, one associated with the R-STA and oneassociated with the R-AP.

If frames arrive that are destined to the R-STA itself, the AP mayindicate a positive TIM for the AID associated with the AID for theR-STA and assign a shorter UL time slot that is sufficient for the R-STAto send a PS-Poll frame to retrieve its own DL data.

If frames arrive that are destined for the group of end-STAs associatedwith the R-AP, the AP may indicate a positive TIM for the AID associatedwith the AID for the R-AP and assign a longer UL time slot that may besufficient for the R-STA to retrieve all frames buffered for allend-STAs associated with it.

In a first alternative, the UL time slot may be sufficient for the R-STAto retrieve all frames buffered for all end-STAs associated with it andthen send out a beacon for the relay BSS indicating a positive TIM forthe end-STAs using the R-AP AIDs.

In a second alternative, the UL time slot may be sufficient for the R-STA to retrieve all frames buffered for all end-STAs associated with itand then send out a beacon for the relay BSS indicating a positive TIMfor the end-STAs using the R-AP assigned AIDs, and for all the end-STAsto send PS-Poll frames to retrieve the frames buffered for them at theR-AP.

If there is only one frame buffered for a particular end-STA that isassociated with a R-AP at the time of the TIM indication, when the R-STAtransmits a PS-Poll frame to the AP to retrieve the DL data frame forits end-STAs, the AP may send the buffered frame using a four-addressMAC frame with the immediate receiver being the R-STA. The R-AP may thenforward the frame to the end-STA using the normal MAC frame format.

If there are multiple frames buffered for end-STAs that are associatedwith a R-AP at the time of the TIM indication, when the R-STA transmitsa PS-Poll frame to the AP to retrieve the DL data frames for itsend-STAs, the AP may send the buffered frames using a multi-user A-MPDUcontaining all frames that are destined for the R-AP's end-STAs. TheR-AP may then forward the frames to the end-STA using an aggregate MACservice data unit (A-MSDU), an A-MPDU, or through the normal positiveTIM and data retrieval process.

Several solutions to address the various problems/aspects of the ACKmechanism and/or procedures for range extension/relay are described.

The ACK mechanism for A-MSDU transmission depends on the direction (tothe distribution system (DS) or from the DS) and relay node'stransmission scheme of data frame to destination node.

In the scenario where the AP sends an A-MSDU containing data for severalSTAs to the relay node, one way to reduce the receiver power consumptionin the destination node is for the relay node to break up the A-MSDUinto individual data frames for each recipient and send them to eachintended recipient/STA one by one. In this scenario, the relay node setsthe partial AID (PAID) subfield in the SIG field of each data frame tothe PAID of the destination node. When the source node detects a dataframe with a PAID that matches one of PAIDs of the A-MSDU (according tothe mapping between the AID and the MAC address of the destinationnode), it knows that the transmission from the source node to the relaynode succeeded. Hence, the PAID serves as an implicit ACK to the sourcenode/AP.

FIG. 18 is a signal diagram for an implicit ACK method 1800 for anA-MSDU from the DS. The method 1800 is performed between an AP 1802, arelay node 1804, a STA i 1806 and a STA j 1808. The AP 1802 sends a DLA-MSDU frame 1810 with the ACK indication bits set to “11,” so thatother STAs can expect that another data frame will follow. After a SIFSinterval 1812, the AP 1802 receives a PHY SIG field with the ACKindication bits set to “00” and checks the PAID subfield in the SIGfield.

The relay node 1804 sends a data frame 1814 for the STA i 1806 with theACK indication bits set to “00” and with a MCS no greater than the MCSused between the AP 1802 and the relay node 1804 and sets the addressfields appropriately. If the STA i 1806 successfully receives the dataframe 1814, then after a SIFS interval 1816, the STA i 1806 sends an ACKframe 1818 to the relay node 1804 with the ACK indication bits set to“10.”

After a SIFS interval 1820, the relay node 1804 sends a data frame 1822for the STA j 1808 with the ACK indication bits set to “00” and with aMCS no greater than the MCS used between the AP 1802 and the relay node1804 and sets the address fields appropriately. If the STA j 1808successfully receives the data frame 1822, then after a SIFS interval1824, the STA j 1808 sends an ACK frame 1826 to the relay node 1804 withthe ACK indication bits set to “10.”

In another scenario, the AP sends an A-MSDU containing data for severalSTAs to the relay node. One way to reduce the signaling overhead andchannel access contention is that the relay node forwards the A-MSDU toall the destination STAs. To facilitate the implicit ACK to the sourcenode, a group ID may be used to indicate the group of STAs that areincluded in the A-MSDU. Usually, the group IDs are maintained andannounced by the root AP. With the relay system, each relay node mayalso maintain and announce its own group ID. In this way, more groupsmay be formed within one BSS. The relay node sets the PAID subfield inthe SIG field of an A-MSDU frame to the destination node to thecorresponding group ID. When the source node detects a data frame whosePAID subfield in the SIG field matches the group of the A-MSDU framethat it transmitted to the relay node, it knows that the transmissionfrom the source node to the relay node succeeded. Hence, the PAID servesas an implicit ACK to the source node/AP.

FIG. 19 is a signal diagram for an alternate implicit ACK method 1900for an A-MSDU from the DS. The method 1900 is performed between an AP1902, a relay node 1904, a STA i 1906 and a STA j 1908. The AP 1902sends a DL A-MSDU frame 1910 with the ACK indication bits set to “11,”so that other STAs can expect that another data frame will follow. Aftera SIFS interval 1912, the AP 1902 receives a PHY SIG field with the ACKindication bits set to “00” and checks the PAID subfield in the SIGfield.

The relay node 1904 sends an A-MSDU frame 1914 for the group of STAs(STA i 1906 and STA j 1908) with the ACK indication bits set to “00” andwith a MCS no greater than the MCS used between the AP 1902 and therelay node 1904 and sets the PAID subfield in the SIG field to becorresponding group ID. If the STA i 1906 successfully receives theA-MSDU frame 1914, then after a SIFS interval 1916, the STA i 1906 sendsan ACK frame 1918 to the relay node 1904 with the ACK indication bitsset to “10.” If the STA j 1908 successfully receives the A-MSDU frame1914, then after a SIFS interval 1920, the STA j 1908 sends an ACK frame1922 to the relay node 1904 with the ACK indication bits set to “10.”

To save signaling overhead and latency for data transmission in a 1 MHzmode relay (where there is no PAID subfield in the SIG field),implicitly signaling the ACK from the relay node to the source node isproposed.

The source node has the knowledge of the destination node's MAC addressand AID or BSSID at the time of association/re-association. The sourcenode sends the DL data frame with the ACK indication bits set to 11, sothat other STAs can expect that another data frame will follow.

The relay node sends the data frame to the destination node with a MCSno greater than the MCS used between the source node and the relay node.In other words, the MAC used between the relay node and the destinationnode is more robust than that used between the source node and the relaynode. The relay node sets the RA field to the MAC address of thedestination node in the MAC header of the data frame.

Within a SIFS time, the source node receives a PHY SIG field with theACK indication bits set to 00, and checks the RA subfield in the MACheader. If the RA subfield in the MAC header matches the destinationnode's MAC address, it knows that the transmission from the source nodeto the relay node succeeded. Hence, the PAID serves as an implicit ACKto the source node/AP.

FIG. 20 is a signal diagram for an implicit ACK method 2000 for a 1 MHzmode relay. The method 2000 is performed between a source node 2002, arelay node 2004, and a destination node 2006. The source node 2002 sendsa data frame 2010 to the relay node 2004, with the ACK indication bitsset to “11,” so that other STAs can expect that another data frame willfollow. After a SIFS interval 2012, the source node 2002 receives a PHYSIG field with the ACK indication bits set to “00” and checks the RAsubfield in the MAC header.

The relay node 2004 sends the data frame as a data frame 2014 for thedestination node 2006 with the ACK indication bits set to “00” and witha MCS no greater than the MCS used between the source node 2002 and therelay node 2004 and sets the RA subfield in the MAC header to the MACaddress of the destination node 2006. If the destination node 2006successfully receives the data frame 2014, then after a SIFS interval2016, the destination node 2006 sends an ACK frame 2018 to the relaynode 2004 with the ACK indication bits set to “10.”

Alternatively, a direction indication bit is added to the SIG field ofthe PLCP header, which may be used as the implicit ACK. The source nodesends the DL data frame with the ACK indication bits set to 11, so thatother STAs can expect that another data frame will follow. The relaynode sends/forwards the data frame to the destination node using adirection indication bit set to the same direction (to the DS or fromthe DS) as the direction of the transmission from the source node to therelay node. Within a SIFS time, if the source node receives a PHY SIGfield with the ACK indication bits set to 00 and the directionindication bit set to the same direction as the direction of thetransmission from the source node to the relay node, it knows that thetransmission from the source node to the relay node succeeded. Hence,the direction indication bit in the SIG field serves as an implicit ACKto the source node.

FIG. 21 is a signal diagram for an alternate implicit ACK method 2100for a 1 MHz mode relay. The method 2100 is performed between a sourcenode 2102, a relay node 2104, and a destination node 2106. The sourcenode 2102 sends a data frame 2110 to the relay node 2104, with the ACKindication bits set to “11,” so that other STAs can expect that anotherdata frame will follow. After a SIFS interval 2112, the source node 2102receives a PHY SIG field with the ACK indication bits set to “00” andthe direction indication bit set to the same direction as the directionof the transmission from the source node 2102 to the relay node 2104.

The relay node 2104 sends the data frame as a data frame 2114 for thedestination node 2106 with the ACK indication bits set to “00” and thedirection indication bit set to the same direction as the direction ofthe transmission from the source node 2102 to the relay node 2104. Ifthe destination node 2106 successfully receives the data frame 2114,then after a SIFS interval 2116, the destination node 2106 sends an ACKframe 2118 to the relay node 2104 with the ACK indication bits set to“10.”

Certain STA types or applications may require that the source node knowsthat the data frame is delivered to the destination node successfullybefore it can flush its transmitter data buffer and go back to sleep.For those STAs or applications, the relay nodes will not send an ACKframe to the source node until it receives an ACK frame from thedestination node.

The source node sends the data frame with the ACK indication bits set to“11,” so that other STAs can expect that another data frame will follow.If the relay node receives the data frame successfully, it sends thedata frame to the destination node using an appropriate MCS. If thedestination node receives the data frame successfully, it sends an ACKframe back to the relay node. Upon receiving the ACK frame from thedestination node, the relay node sends an ACK frame back to the sourcenode.

FIG. 22 is a signal diagram of an ACK forwarding method 2200. The method2200 is performed between a source node 2202, a relay node 2204, and adestination node 2206. The source node 2202 sends a data frame 2210 tothe relay node 2204, with the ACK indication bits set to “11,” so thatother STAs can expect that another data frame will follow. After a SIFSinterval 2212, the relay node 2204 sends the data frame as a data frame2214 for the destination node 2206 with the ACK indication bits set to“00.” When the relay node 2204 sends the data frame 2214, the sourcenode 2202 determines a new ACK timing 2216. There is no signaling forthe source node 2202 to receive the new ACK timing 2216; the source node2202 knows that if relay is used, the ACK timing 2216 will be different(or longer) than non-relay data transmission.

If the destination node 2206 successfully receives the data frame 2214,then after a SIFS interval 2218, the destination node 2206 sends an ACKframe 2220 to the relay node 2204. Upon receiving the ACK frame 2220from the destination node 2206, after a SIFS interval 2222, the relaynode 2204 sends an ACK frame 2224 to the source node 2202.

In one scenario, several STAs send data frames to a relay node. Thosedata frames may be transmitted to the relay node in sequential order inthe time domain or in a frequency, code, or spatial orthogonal manner.When one of the STAs sends a control frame requesting a block ACK to therelay node, the relay node either sends back a block ACK frame before itforwards the data frames to the AP or the relay node assembles thosedata frames into an A-MSDU frame and sends the A-MSDU frame to thedestination node (or AP). This block ACK may be a multiuser ACK. If therelay node sends the assembled data frames in an A-MSDU frame, a groupID may be used to indicate the group of STAs that are included in theA-MSDU frame. The relay node sets the PAID subfield in the SIG field ofthe A-MSDU frame to the destination node to the corresponding group ID.When the source node detects a data frame whose PAID subfield in the SIGfield matches the group that it belongs to, it knows that thetransmission from the source node to the relay node succeeded. Hence,the PAID serves as an implicit block ACK to the source nodes.

An end-to-end block ACK scheme for a STA using range extension or relaymay be used. The source node first performs end-to-end add trafficstream (addTS)/add block ACK (addBA) operations with the destinationnode through the relay node.

The source node sends packets using a delayed BA mechanism, and sets theACK indication in the PLCP header to “11” or “10.” Upon successfulreceipt of data frames from the source node, the relay node does notsend an ACK, but sends data frames to the destination node.

When the source node finishes the transmission, it may enter a sleepmode if it is a non-AP STA. When the source node awakes from sleep, itmay send a four-address format block ACK request (BAR) frame to therelay node. The four- address BAR frame is a new frame format. The relaynode forwards the BAR frame to the destination node. The destinationnode sends a four-address BA frame, which is also a new frame format.

FIG. 23 is a signal diagram of an end-to-end block ACK method 2300. Themethod 2300 is performed between a source node 2302, a relay node 2304,and a destination node 2306. The source node 2302 sends several dataframes 2310, with the ACK indication bits of each data frame set to“11,” so that other STAs can expect that another data frame will followor to “10,” meaning that no ACK is required.

After sending the data frames 2310, the source node 2302 may enter asleep mode is it is a non-AP STA (step 2312). Upon receiving the dataframes 2310, the relay node 2304 sends the data frames as data frames2314 for the destination node 2306. If the source node 2302 is a non-APSTA and exits the sleep mode, it sends a block ACK request (BAR) frame2316 to the relay node 2304. If the source node 2302 is an AP, then thesource node 2302 can estimate the timing for the relay node 2304 tofinish the data block transmission and after this estimated time, sendsthe BAR frame 2316 to the relay node 2304. Upon receiving the BAR frame2316, the source node 2302 sends a BAR frame 2318 to the destinationnode 2306. The destination node 2306 response with a BA frame 2320. Therelay node 2304 then sends a BA frame 2322 to the source node 2302.

The following methods may be used to facilitate the Speed Frame Exchangefor relay operation. In a first method, a relay frame field is used tocontrol the Speed Frame Exchange procedures for relay. Upon receiving adata frame from the source node with a More Data field set to “1,” therelay node may choose to continue the Speed Frame Exchange between thesource node and the relay node, and forward the received data frame(s)to the destination node later. The relay node transmits an ACK frame (toacknowledge the received data frame) with the Relayed Frame field set to“0.” A source node that receives the ACK frame that matches its MACaddress with the Relayed Frame field set to “0” may continue its dataframe transmission within the current TXOP if it has more data totransmit. Upon receiving the ACK frame that matches its address with theRelayed Frame field set to “0,” the source node transmits a data frame aSIFS interval after the received ACK frame.

Two examples are described below. In a first example, the relay nodesets the Relayed Frame field to “1” after receiving the second dataframe from the source node with the More Data field equal to “0”. Therelay node forwards the received data frames to the destination node ona one-by-one basis.

FIG. 24 is a signal diagram of the first example of a speed frameexchange method 2400 for relay. The method 2400 is performed between asource node 2402, a relay node 2404, and a destination node 2406. Thesource node 2402 sends a first data frame 2410 to the relay node 2404,with the More Data field set to “1,” to indicate to the relay node 2404that the source node 2402 has more data frames to transmit. After a SIFSinterval 2412, the relay node 2404 sends an ACK frame 2414 to the sourcenode 2402, with the More Data field set to “0” and the Relayed Framefield set to “0.” After a SIFS interval 2416, the source node 2402 sendsa second data frame 2418 to the relay node 2404, with the More Datafield set to “0,” to indicate that the source node 2402 does not haveany more data frames to transmit.

After a SIFS interval 2420, the relay node 2404 sends an ACK frame 2422to the source node 2402, with the More Data field set to “0” and theRelayed Frame field set to “1.” After a SIFS interval 2424, the relaynode 2404 sends the first data frame as data frame 2426 to thedestination node 2406, with the Relayed Frame field set to “1.” After aSIFS interval 2428, the destination node sends an ACK frame 2430 to therelay node 2404. After receiving the ACK frame 2430, the relay node 2404waits for a SIFS interval (not shown in FIG. 24) before sending thesecond data frame as data frame 2432.

Similarly, in a second example, the relay node sets the Relayed Framefield to “1” after receiving the second data frame from the source nodewith the More Data field equal to “0”. The relay node aggregates thereceived data frames into one A-MSDU and forwards the A-MSDU to thedestination node.

FIG. 25 is a signal diagram of the second example of a speed frameexchange method 2500 for relay. The method 2500 is performed between asource node 2502, a relay node 2504, and a destination node 2506. Thesource node 2502 sends a first data frame 2510 to the relay node 2504,with the More Data field set to “1,” to indicate to the relay node 2504that the source node 2502 has more data frames to transmit. After a SIFSinterval 2512, the relay node 2504 sends an ACK frame 2514 to the sourcenode 2502, with the More Data field set to “0” and the Relayed Framefield set to “0.” After a SIFS interval 2516, the source node 2502 sendsa second data frame 2518 to the relay node 2504, with the More Datafield set to “0,” to indicate that the source node 2502 does not haveany more data frames to transmit.

After a SIFS interval 2520, the relay node 2504 sends an ACK frame 2522to the source node 2502, with the More Data field set to “0” and theRelayed Frame field set to “1.” After a SIFS interval 2524, the relaynode 2504 sends the first data frame and the second data frame as anA-MSDU frame 2526 to the destination node 2506, with the Relayed Framefield set to “1.” After a SIFS interval 2528, the destination node sendsan ACK frame 2530 to the relay node 2504.

Alternately, upon receiving a data frame from the source node with aMore Data field set to “1,” the relay node may choose not to continuethe Speed Frame Exchange between the source node and the relay node, andimmediately forward the received data frame to the destination node. Therelay node transmits an ACK frame (to acknowledge the received dataframe) with the Relayed Frame field set to “1.” A source node thatreceives the ACK frame that matches its address with the Relayed Framefield set to “1” does not initiate any further frame transmission withinthe current TXOP.

In a second method to facilitate the Speed Frame Exchange for relayoperation, a new one-bit field called “Speed Frame Exchange Continue”(SFEC) may be defined in the ACK frame to control the Speed FrameExchange procedures for relay. In this method, the source node and therelay node follow the procedures below.

Upon receiving a data frame from the source node with the More Datafield set to “1,” the relay node may choose to continue the Speed FrameExchange between the source node and the relay node, and forward thereceived data frame(s) to the destination node later. The relay nodetransmits an ACK frame (to acknowledge the received data frame) with theSFEC field set to “1.” A source node that receives the ACK frame thatmatches its MAC address with SFEC field set to “1” may continue its dataframe transmission within the current TXOP if it has more data totransmit. Upon receiving the ACK frame that matches its address withSFEC field set to “1,” the source node transmits a data frame a SIFStime after the received ACK frame.

Two examples are described below. In the first example, the relay nodesets the SFEC field to “0” after receiving the second data frame fromthe source node with the More Data field set to “0.” The relay nodeforwards the received data frames to the destination node on aone-by-one basis.

FIG. 26 is a signal diagram of the first example of a speed frameexchange method 2600 for relay using the SFEC field. The method 2600 isperformed between a source node 2602, a relay node 2604, and adestination node 2606. The source node 2602 sends a first data frame2610 to the relay node 2604, with the More Data field set to “1,” toindicate to the relay node 2604 that the source node 2602 has more dataframes to transmit. After a SIFS interval 2612, the relay node 2604sends an ACK frame 2614 to the source node 2602, with the More Datafield set to “0” and the SFEC field set to “1.” After a SIFS interval2616, the source node 2602 sends a second data frame 2618 to the relaynode 2604, with the More Data field set to “0,” to indicate that thesource node 2602 does not have any more data frames to transmit.

After a SIFS interval 2620, the relay node 2604 sends an ACK frame 2622to the source node 2602, with the More Data field set to “0” and theSFEC field set to “0.” After a SIFS interval 2624, the relay node 2604sends the first data frame as data frame 2626 to the destination node2606, with the Relayed Frame field set to “1.” After a SIFS interval2628, the destination node sends an ACK frame 2630 to the relay node2604. After receiving the ACK frame 2630, the relay node 2604 waits fora SIFS interval (not shown in FIG. 26) before sending the second dataframe as data frame 2632.

Similarly, in a second example, the relay node sets the SFEC field to“0” after receiving the second data frame from the source node with theMore Data field set to “0.” The relay node aggregates the received dataframes into one A-MSDU and forwards the A-MSDU to the destination node.

FIG. 27 is a signal diagram of the second example of a speed frameexchange method 2700 for relay using the SFEC field. The method 2700 isperformed between a source node 2702, a relay node 2704, and adestination node 2706. The source node 2702 sends a first data frame2710 to the relay node 2704, with the More Data field set to “1,” toindicate to the relay node 2704 that the source node 2702 has more dataframes to transmit. After a SIFS interval 2712, the relay node 2704sends an ACK frame 2714 to the source node 2702, with the More Datafield set to “0” and the SFEC field set to “1.” After a SIFS interval2716, the source node 2702 sends a second data frame 2718 to the relaynode 2704, with the More Data field set to “0,” to indicate that thesource node 2702 does not have any more data frames to transmit.

After a SIFS interval 2720, the relay node 2704 sends an ACK frame 2722to the source node 2702, with the More Data field set to “0” and theSFEC field set to “0.” After a SIFS interval 2724, the relay node 2704sends the first data frame and the second data frame as an A-MSDU frame2726 to the destination node 2706, with the Relayed Frame field set to“1.” After a SIFS interval 2728, the destination node sends an ACK frame2730 to the relay node 2704.

Alternately, upon receiving a data frame from the source node with theMore Data field set to “1,” the relay node may choose not to continuethe Speed Frame Exchange between the source node and the relay node andforward the received data frame to the destination immediately. Therelay node transmits an ACK frame with the SFEC field set to “0.” Asource node that receives the ACK frame that matches its MAC addresswith the SFEC field set to “0” does not initiate any further frametransmission within the current TXOP.

In the methods 2600 and 2700, the Relayed Frame field may be included inthe ACK frame. The relay node may set the Relayed Frame field to “1,”and the source node interprets this as an indication that the currentTXOP is shared with the R-STA using an explicit ACK procedure. Thesource node relies on the SFEC field to determine whether to continuethe Speed Frame Exchange procedures or not.

The methods 2400, 2500, 2600, and 2700 may be applicable to the SpeedFrame Exchange between the relay node and the destination node as well.

In the methods 2400, 2500, 2600, and 2700, the source node may be anon-AP STA or an AP. The NDP ACK frame may be used in the methods 2400,2500, 2600, and 2700 instead of the regular ACK. In the case where theNDP ACK is used, the transmitter/source node calculates the ACK ID usingthe same formula as the receiver/responder/relay node (i.e., using thepartial FCS and the information from the scrambling seed in the SERVICEfield of the frame being acknowledged), and check whether the ACK ID inthe received NDP ACK frame matches the ACK ID calculated at thetransmitter/source node. If it matches, the received NDP ACK frame isconsidered as a matched ACK (equivalent to the RA field of the regularACK frame matching the transmitter's address).

In the case where the NDP block ACK frame is used, the transmittercompares the block ACK ID in the received NDP block ACK frame with the Nleast significant bits (LSBs) of the PLCP data scrambler of the PSDUthat carries the soliciting A-MPDU or the BAR. If they match, then thereceived NDP block ACK frame is considered to be a matched block ACKframe.

In the case where the NDP modified ACK frame is used to respond to a NDPPS-Poll frame, the transmitter of the NDP PS-Poll frame calculates theACK ID using the same formula as the receiver/responder (using the RA,TA, and CRC fields of received NDP PS-Poll frame), and compares it withthe ACK ID in the received NDP modified ACK frame. If they match, thenthe received NDP modified ACK frame is considered to be a matched NDPmodified ACK frame.

The NDP ACK, NDP block ACK, and NDP modified ACK matching conditions andprocedures are not limited to relay operation, and may be applicable toall STAs (AP and non-AP) that use NDP ACK, NDP block ACK, and NDPmodified ACK frames.

Currently, a R-AP that is associated with a root AP may acceptassociations from end-STAs. However, a root AP has no means to controlthe association behavior of the R-APs that are associated with it, andthe association behavior for the R-APs may have an impact on systemperformance. Therefore, methods to control the association behavior ofthe R-APs are desirable.

A root AP, or any other controlling entity such as a centralized controlAP, may provide control and constraints for the association behavior ofthe R-APs that are associated with it, to provide better control ofsystem performance. An end-STA may also provide requirements on theR-AP.

A root AP, or any other controlling entity, may use a Relay Control IEto control and constrain the behavior, such as the association behavior,of R-APs that are associated with it. An end-STA may also use a RelayControl IE to specify its requirements for a R-AP. A R-AP may also usethe Relay Control IE to specify its own operation, constraints, etc. TheRelay Control IE may be used in connection with any of the embodimentsdescribed herein.

FIG. 28 is a diagram of a Relay Control IE format 2800. The RelayControl IE 2800 includes an element ID field 2802, a length field 2804,a number of relays field 2806, a number of current relays field 2808, arelay capabilities field 2810, a number of end-STAs field 2812, anend-STA types field 2814, an end-STA capabilities field 2816, an end-STAtraffic specification (spec) field 2818, and a relay gains field 2820.

The element ID field 2802 identifies the Relay Control IE 2800 as aRelay Control IE. The length field 2804 indicates the length of theRelay Control IE 2800. The number of relays field 2806 includes thetotal number of allowable R-APs that are allowed to associate with thecurrent root AP or the transmitting STA.

The number of current relays field 2808 includes the number of R-APsthat are currently associated with the root AP or the transmitting STA.In one implementation (not shown in FIG. 28), the number of relays field2806 and the number of current relays field 2808 may be combined intoone field called (for example) Allowed Additional Relays, whichindicates the maximum additional number of R-APs that are allowed toassociate with the root AP or the transmitting STAs.

The relay capabilities field 2810 specifies the capabilities that a R-APmay support or is required to support. The relay capabilities field 2810may be implemented as a bitmap with a positive “1” indicating thesupport or the need to support a certain capability associated with thebit. Such capabilities may include: sectorized operation, Type 0 or Type1 sectorization, transmit power control, coordination, synchronizationfor end-STA, RAW, Periodic RAW (PRAW), target wake time (TWT),Subchannel Selective Transmission (SST), etc.

The number of end-STAs field 2812 specifies the maximum number ofend-STAs that a R-AP is allowed to provide association to. The end-STAtypes field 2814 specifies the type(s) of end-STAs that the R-AP isallowed to provide association to. The end-STA types specified mayinclude: sensors, event-driven sensors, energy-limited STA, 1 MHz STAs,2 MHz and above STAs, SST STAs, STAs using sectorized operations, HEWSTAs, legacy STAs, or all types of STAs.

The end-STA capabilities field 2816 specifies the capabilities that anend-STA must support to be associated with the R-AP. The end-STAcapabilities field 2816 may be implemented as a bitmap with a positive“1” indicating the support or the need to support a certain capabilityassociated with the bit. Such capabilities may include: sectorizedoperation, Type 0 or Type 1 sectorization, transmit power control,coordination, synchronization for end-STA, RAW, PRAW, TWT, SubchannelSelective Transmission (SST), mandatory set of MCS, etc.

The end-STA traffic specification field 2818 specifies the type oftraffic that an end-STA generates to be able to be allowed to associatewith the R-AP. Such a traffic specification may include traffic accesscategories (ACs) and traffic load. The traffic ACs subfield may specifythe type of ACs traffic that a STA generates to be associated with theR-AP. For example, the root AP may specify that only STAs generatingevent report traffic, such as a fire alarm or intruder detection, may besupported by one or more R-APs. In another example, a root AP mayspecify that only STAs generating AC_VI and AC_VO traffic may besupported by one or more R-APs. The traffic load subfield may specifythe traffic load that an end-STA may generate to be associated with theR-AP. For example, the root AP may specify that an end-STA may notgenerate more than 500 kbps on average to be associated with one or moreR-APs. In addition, the traffic load may be specified per AC or usinganother type of specification.

The relay gains field 2820 specifies the threshold for gains when havingtraffic forwarded through a relay node that a STA should obtain to beassociated with the R-AP. This field may include a relay gain categoriessubfield and a relay gain threshold subfield. The relay gain categoriessubfield may include: energy, medium occupation time, aggregation gain,range, etc. The relay gains field 2820 may include multiple relay gaincategories subfields. The relay gain threshold subfield specifies theminimal gain that an end-STA should obtain when sending packets throughthe R-AP instead of sending packets to the root AP directly. The exactimplementation may depend on the relay gain categories. For energy, therelay gain threshold may be specified by integers that specify theenergy saving when transmitting through the R-AP instead of directlytransmitting to the root AP. Each integer may be associated with acertain unit of energy, such as mJ.

The energy usage may be estimated using a packet of a pre-defined sizeor may be the energy consumed to transmit some unit of data. In anotherexample, the relay gain threshold may be specified by integers thatspecify the saving of medium occupation time when transmitting throughthe R-AP instead of directly transmitting to the root AP. Each integermay be associated with a certain unit of time, such as a nanosecond or amicrosecond. The reduction of medium occupation time may be estimatedusing a packet of a pre-defined size or per some units of data.

Any subset of the subfields of the Relay Control IE 2800 may beimplemented as a subfield or subsets of subfields of any existing or newIE, for example, the Relay Element, Relay Operation Element, theS1G/VHT/HEW/VHSE Operation Element, the S1G/VHT/HEW/VHSE CapabilityElement, or as a part of any action frames, action without ACK frames,control, management, or extension frames, such as beacon, short beacon,probe request, probe response, association request, associationresponse, reassociation request, reassociation response, S1G actionframes, HEW action frames, or in MAC/PLCP headers. For example, theinclusion of some of the fields or subfields in the Relay Element may beindicated by a value in the Relay Control field in the Relay Element. Aroot AP, R-AP, or end-STA may include the Relay Control IE in itsbeacon, short beacon, probe request, probe response, associationrequest, association response, reassociation request, reassociationresponse, or any other type of control, management, or extension framesat time of association, reassociation, or at other times.

A root AP may include a Relay Control IE to specify its requirements forthe relay nodes that want to associate with it. For example, the root APmay specify the capabilities that a STA must satisfy to be associated asa R-AP, such as a minimal number of supported end-STAs or sectorizedoperations, SST, etc. The root AP may also indicate how many slots ofR-AP that it has.

A root AP may include a Relay Control IE to control the behavior of theR-AP. For example, the root AP may specify the number of end-STAs thatthe R-AP is allowed to provide association with, and/or the type of theend-STAs, the end-STAs with certain capabilities, and/or the type and/orload of the traffic that an end-STA generates, so that the R-AP mayprovide association to the appropriate end-STAs. In addition to oralternatively, the root AP may specify the gain threshold that a STAmust obtain when it transmits through the R-AP instead of transmittingdirectly to the AP to be able to associate with the R-AP.

A STA that is capable of relaying may include the Relay Control IE inits probe request, association request, reassociation request, or anyother type of control, management, or extension frames to indicate to anAP, which may be a root AP, of its own relaying capabilities.

When a root AP receives a probe request including the Relay Control IEfrom a relaying STA, it may choose not to reply to the request becauseits own capabilities do not match those required by the relaying STA,the capabilities supported by the relaying STA do not match its ownrequirements for R-APs, or the root AP determined that there is notenough gain by associating with the relaying STA as a R-AP. When a rootAP receives an association request or a reassociation request includingthe Relay Control IE from a relaying STA, it may choose to reject therequest because its own capabilities do not match those required by therelaying STA as a root AP, the capabilities supported by the relayingSTA do not match its own requirements for R-APs, or the root APdetermined that there is not enough gain by associating with therelaying STA as a R-AP.

A R-AP that is associated with a root AP may include the Relay ControlIE in its beacon, short beacon, probe response, association response,reassociation response, or any other type of control, management, orextension frames to indicate its relay capabilities and constraints oroperations to STAs, including end-STAs.

An end-STA may include a Relay Control IE in its probe request,association request, reassociation request, or any other control,management, or extension frames to indicate its requirements for a R-AP.For example, the end-STA may specify that a R-AP must have sectorizedoperation capabilities, SST, etc. In another example, an end-STA mayalso specify that a R-AP should support Sensor Only.

When a R-AP receives a probe request including the Relay Control IE froman end-STA, it may choose not to reply to the request because its owncapabilities do not match those required by the end-STA, thecapabilities supported by the end-STA do not match its own requirementsfor end-STAs, or the end-STA would not achieve sufficient gain bytransmitting through the R-AP. When a R-AP receives an associationrequest or a reassociation request including the Relay Control IE froman end-STA, it may choose to reject the request because its owncapabilities do not match those required by the end-STA, thecapabilities supported by the end-STA do not match its own requirementsfor end-STAs, or the end-STA would not achieve sufficient gain bytransmitting through the R-AP.

The exiting design of the Relay Element is not flexible. The root APBSSID subfield is always included, causing extra overhead when there isno need to signal the root AP BSSID. Additionally, the design of therelay element does not allow the transmitter to identify itself as anon-AP R-STA. Therefore, it is desirable to develop an efficient designto allow the use of the relay element in various management frames forrelay (such as beacon, association, and probe request/response frames)to sufficiently support the relay operation.

The Relay Element format may be modified as described below to allowefficient signaling of different cases where the Relay Element istransmitted and for efficient signaling of the RootAP BSSID subfield.The Reply Element format shown and described above in connection withFIG. 4 is modified in that the root AP BSSID field is made optional.

In addition to the two values of the Relay Control subfield alreadydefined in Table 1 above (representing cases 0 and 1), additional valuesof the Relay Control field may be designed to represent one or severalof the following cases/scenarios.

A Relay Control value of “2” may be used to indicate a root AP without aRootAP BSSID field in the Relay Element. For example, this may be usedin the case where the Relay Element is included in the management frames(such as beacon, probe response, association response, or reassociationresponse frames) transmitted by the root AP. In those cases, there is noneed to signal the RootAP BSSID.

A Relay Control value of “3” may be used to indicate a relayed SSIDwithout the RootAP BSSID field in the Relay Element. For example, thismay be used in the case where the Relay Element is included in theassociation response or reassociation response frames (transmitted bythe non-root AP R-AP) where there is no need to signal the RootAP BSSID.

A Relay Control value of “4” may be used to indicate a non-AP STAcapable of relay operation with the RootAP BSSID field in the RelayElement. For example, this may be used in the case where the RelayElement is included in the reassociation request frame where the currentassociated RootAP BSSID is available.

A Relay Control value of “5” may be used to indicate a non-AP STAcapable of relay operation without the RootAP BSSID field in the RelayElement. For example, this may be used in an association request or aprobe request frame.

An example of the values for the Relay Control field is shown in Table2. The actual design of the method may use any order of the RelayControl field values to represent the cases/scenarios or a subset ofcases/scenarios.

TABLE 2 Relay Control Meaning 0 Root AP 1 Relayed SSID 2 Root AP withoutRootAP BSSID subfield in Relay Element 3 Relayed SSID without RootAPBSSID subfield in Relay Element 4 Non-AP STA 5 Non-AP STA without RootAPBSSID subfield 6-255 Reserved

The embodiments described above relate to procedures for support of arelay node, but a relay node may also be considered as a STA whichperforms the procedures described herein to support the functions orrequirements of a relay node.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element may be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andnon-transitory computer-readable storage media. Examples ofnon-transitory computer-readable storage media include, but are notlimited to, a read only memory (ROM), a random access memory (RAM), aregister, cache memory, semiconductor memory devices, magnetic mediasuch as internal hard disks and removable disks, magneto-optical media,and optical media such as CD-ROM disks, and digital versatile disks(DVDs). A processor in association with software may be used toimplement a radio frequency transceiver for use in a WTRU, UE, terminal,base station, RNC, or any host computer.

What is claimed is:
 1. A method for associating a new end-station(end-STA) with a relay access point (R-AP) in a relay transmission, themethod comprising: transmitting an assignment of a new identifier to thenew end-STA, wherein traffic indication map indications for the newend-STA in a beacon from the R-AP follows the transmission of the newidentifier assignment; sending a message to a root access point (AP),the message including: an indication of a number of information fieldsin the message; and at least one information field, each of the at leastone information fields including an identifier of one end-STA associatedwith the R-AP; and receiving an acknowledgement from the root AP on acondition that the root AP correctly receives the message and associatesan identifier of the end-STA with an identifier of the R-AP.
 2. Themethod according to claim 1, wherein the identifier of the end-STAincludes any one of: a medium access control address of the end-STA oran association identifier of the end-STA.
 3. The method according toclaim 1, wherein the new identifier is an association identifier.
 4. Themethod according to claim 1, wherein the identifier of the R-AP includesany one of: a medium access control address of the R-AP or anassociation identifier of the R-AP.
 5. The method according to claim 1,wherein the acknowledgement received from the root AP includes any oneof: an acknowledgement frame or a block acknowledgement frame.
 6. Themethod according to claim 1, wherein the message includes an end-STAinformation element.
 7. A relay access point (R-AP), comprising: aprocessor configured to assign a new identifier to a new end-station(end- STA) associated with the R-AP; a transmitter configured to:transmit the new identifier to the new end-STA, wherein trafficindication map indications for the new end-STA in a beacon from the R-APfollows the transmission of the new identifier assignment; and send amessage to a root access point (AP), the message including: anindication of a number of information fields in the message; and atleast one information field, each of the at least one information fieldsincluding an identifier of one end-STA associated with the R-AP; and areceiver configured to receive an acknowledgement from the root AP on acondition that the root AP correctly receives the message and associatesan identifier of the end-STA with an identifier of the R-AP.
 8. The R-APaccording to claim 7, wherein the identifier of the end-STA includes anyone of: a medium access control address of the end-STA or an associationidentifier of the end-STA.
 9. The R-AP according to claim 7, wherein thenew identifier is an association identifier.
 10. The R-AP according toclaim 7, wherein the identifier of the R-AP includes any one of: amedium access control address of the R-AP or an association identifierof the R-AP.
 11. The R-AP according to claim 7, wherein theacknowledgement received from the root AP includes any one of: anacknowledgement frame or a block acknowledgement frame.
 12. The R-APaccording to claim 7, wherein the message includes an end- STAinformation element.
 13. An information element (IE) for use in a relaytransmission, comprising: an indication of a number of informationfields in the IE; and each information field including an identifier ofone end-station (end-STA).
 14. The IE according to claim 13, wherein theidentifier includes any one of: a medium access control address of theend-STA or an association identifier of the end-STA.
 15. The IEaccording to claim 13, wherein each information field further includes:a previous association indication of the end-STA, which is a device thatthe end-STA was previously associated with; and a previous associationidentifier (AID) of the end-STA, which is the AID of a root access point(AP) that the end-STA was previously associated with.
 16. The IEaccording to claim 15, wherein the device includes any one of: an AP, arelay AP, or a root AP.
 17. The IE according to claim 15, wherein theprevious association indication includes a medium access control addressof the device.
 18. A method for use in a relay access point (R-AP),comprising: communicating with a plurality of end-stations (end-STAs),each end-STA having a medium access control (MAC) address; determiningthat a new end-STA has associated with the R-AP; generating a messagefor transmission to a root access point (AP), the message including aMAC address of each of the plurality of end-STAs and a MAC address ofthe new end-STA; and transmitting the message to the root AP.
 19. Themethod according to claim 18, wherein the message further includes afield containing a number of end-STAs communicating with the R-AP,wherein the number includes the plurality of end-STAs and the newend-STA.